Programs & Examples On #Ecl

Embeddable Common Lisp (ECL) is an open source Common Lisp implementation aimed at producing a small-footprint Lisp system that can be integrated with C-based applications.

Monitoring the Full Disclosure mailinglist

Two generic ways to do the same thing... I'm not aware of any specific open solutions to do this, but it'd be rather trivial to do.

You could write a daily or weekly cron/jenkins job to scrape the previous time period's email from the archive looking for your keyworkds/combinations. Sending a batch digest with what it finds, if anything.

But personally, I'd Setup a specific email account to subscribe to the various security lists you're interested in. Add a simple automated script to parse the new emails for various keywords or combinations of keywords, when it finds a match forward that email on to you/your team. Just be sure to keep the keywords list updated with new products you're using.

You could even do this with a gmail account and custom rules, which is what I currently do, but I have setup an internal inbox in the past with a simple python script to forward emails that were of interest.

How do I get the command-line for an Eclipse run configuration?

You'll find the junit launch commands in .metadata/.plugins/org.eclipse.debug.core/.launches, assuming your Eclipse works like mine does. The files are named {TestClass}.launch.

You will probably also need the .classpath file in the project directory that contains the test class.

Like the run configurations, they're XML files (even if they don't have an xml extension).

conflicting types for 'outchar'

In C, the order that you define things often matters. Either move the definition of outchar to the top, or provide a prototype at the top, like this:

#include <stdio.h> #include <stdlib.h>  void outchar(char ch);  int main() {     outchar('A');     outchar('B');     outchar('C');     return 0; }  void outchar(char ch) {     printf("%c", ch); } 

Also, you should be specifying the return type of every function. I added that for you.

How to make a variable accessible outside a function?

Your variable declarations and their scope are correct. The problem you are facing is that the first AJAX request may take a little bit time to finish. Therefore, the second URL will be filled with the value of sID before the its content has been set. You have to remember that AJAX request are normally asynchronous, i.e. the code execution goes on while the data is being fetched in the background.

You have to nest the requests:

$.getJSON(""+input+"?api_key=API_KEY_HERE"  , function(name){   obj = name;   // sID is only now available!   sID =;   console.log(sID); }); 

Clean up your code!

  • Put the second request into a function
  • and let it accept sID as a parameter, so you don't have to declare it globally anymore! (Global variables are almost always evil!)
  • Remove sID and obj variables - is sufficient unless you really need the other variables outside the function.

$.getJSON(""+input+"?api_key=API_KEY_HERE"  , function(name){   // We don't need sID or obj here - is sufficient   console.log(;    doSecondRequest(; });  /// TODO Choose a better name function doSecondRequest(sID) {   $.getJSON("" + sID + "/summary?api_key=API_KEY_HERE", function(stats){         console.log(stats);   }); } 

Hapy New Year :)

python variable NameError

I would approach it like this:

sizes = [100, 250] print "How much space should the random song list occupy?" print '\n'.join("{0}. {1}Mb".format(n, s)                 for n, s in enumerate(sizes, 1)) # present choices choice = int(raw_input("Enter choice:")) # throws error if not int size = sizes[0] # safe starting choice if choice in range(2, len(sizes) + 1):     size = sizes[choice - 1] # note index offset from choice print "You  want to create a random song list that is {0}Mb.".format(size) 

You could also loop until you get an acceptable answer and cover yourself in case of error:

choice = 0 while choice not in range(1, len(sizes) + 1): # loop     try: # guard against error         choice = int(raw_input(...))     except ValueError: # couldn't make an int         print "Please enter a number"         choice = 0 size = sizes[choice - 1] # now definitely valid 

My eclipse won't open, i download the bundle pack it keeps saying error log

Make sure you have the prerequisite, a JVM ( installed.

This will be a JRE and JDK package.

There are a number of sources which includes:

Passing multiple values for same variable in stored procedure

Your stored procedure is designed to accept a single parameter, Arg1List. You can't pass 4 parameters to a procedure that only accepts one.

To make it work, the code that calls your procedure will need to concatenate your parameters into a single string of no more than 3000 characters and pass it in as a single parameter.

Please help me convert this script to a simple image slider

Problems only surface when I am I trying to give the first loaded content an active state

Does this mean that you want to add a class to the first button?

$('.o-links').click(function(e) {   // ... }).first().addClass('O_Nav_Current'); 

instead of using IDs for the slider's items and resetting html contents you can use classes and indexes:


.image-area {     width: 100%;     height: auto;     display: none; }  .image-area:first-of-type {     display: block; } 


var $slides = $('.image-area'),     $btns = $('a.o-links');  $btns.on('click', function (e) {     var i = $btns.removeClass('O_Nav_Current').index(this);     $(this).addClass('O_Nav_Current');      $slides.filter(':visible').fadeOut(1000, function () {         $slides.eq(i).fadeIn(1000);     });      e.preventDefault();  }).first().addClass('O_Nav_Current');

Highlight Anchor Links when user manually scrolls?

You can use Jquery's on method and listen for the scroll event.

Hadoop MapReduce: Strange Result when Storing Previous Value in Memory in a Reduce Class (Java)

It is very inefficient to store all values in memory, so the objects are reused and loaded one at a time. See this other SO question for a good explanation. Summary:

[...] when looping through the Iterable value list, each Object instance is re-used, so it only keeps one instance around at a given time.

Real time face detection OpenCV, Python

Your line:

img = cv2.rectangle(img,(x,y),(x+w,y+h),(255,0,0),2) 

will draw a rectangle in the image, but the return value will be None, so img changes to None and cannot be drawn.



error TS1086: An accessor cannot be declared in an ambient context in Angular 9

Adding skipLibCheck: true in compilerOptions inside tsconfig.json file fixed my issue.

"compilerOptions": {
   "skipLibCheck": true,

TS1086: An accessor cannot be declared in ambient context

I've updated typescript and tslint versions and removed packages I wasn't using. This solved the problem for me.

As others pointed here, it seems to be an issue with different TypeScript versions where the generated typings from some library aren't compatible with your TypeScript version.

Has been compiled by a more recent version of the Java Runtime (class file version 57.0)

I had similar problem with IntelliJ when tried to run some Groovy scripts. Here is how I solved it.

Go to "Project Structure"-> "Project" -> "Project language level" and select "SDK default". This should use the same SDK for all project modules.

Understanding esModuleInterop in tsconfig file

Problem statement

Problem occurs when we want to import CommonJS module into ES6 module codebase.

Before these flags we had to import CommonJS modules with star (* as something) import:

// node_modules/moment/index.js
exports = moment
// index.ts file in our app
import * as moment from 'moment'
moment(); // not compliant with es6 module spec

// transpiled js (simplified):
const moment = require("moment");

We can see that * was somehow equivalent to exports variable. It worked fine, but it wasn't compliant with es6 modules spec. In spec, the namespace record in star import (moment in our case) can be only a plain object, not callable (moment() is not allowed).


With flag esModuleInterop we can import CommonJS modules in compliance with es6 modules spec. Now our import code looks like this:

// index.ts file in our app
import moment from 'moment'
moment(); // compliant with es6 module spec

// transpiled js with esModuleInterop (simplified):
const moment = __importDefault(require('moment'));

It works and it's perfectly valid with es6 modules spec, because moment is not namespace from star import, it's default import.

But how does it work? As you can see, because we did a default import, we called the default property on a moment object. But we didn't declare a default property on the exports object in the moment library. The key is the __importDefault function. It assigns module (exports) to the default property for CommonJS modules:

var __importDefault = (this && this.__importDefault) || function (mod) {
    return (mod && mod.__esModule) ? mod : { "default": mod };

As you can see, we import es6 modules as they are, but CommonJS modules are wrapped into an object with the default key. This makes it possible to import defaults on CommonJS modules.

__importStar does the similar job - it returns untouched esModules, but translates CommonJS modules into modules with a default property:

// index.ts file in our app
import * as moment from 'moment'

// transpiled js with esModuleInterop (simplified):
const moment = __importStar(require("moment"));
// note that "moment" is now uncallable - ts will report error!
var __importStar = (this && this.__importStar) || function (mod) {
    if (mod && mod.__esModule) return mod;
    var result = {};
    if (mod != null) for (var k in mod) if (, k)) result[k] = mod[k];
    result["default"] = mod;
    return result;

Synthetic imports

And what about allowSyntheticDefaultImports - what is it for? Now the docs should be clear:

Allow default imports from modules with no default export. This does not affect code emit, just typechecking.

In moment typings we don't have specified default export, and we shouldn't have, because it's available only with flag esModuleInterop on. So allowSyntheticDefaultImports will not report an error if we want to import default from a third-party module which doesn't have a default export.

Why am I getting Unknown error in line 1 of pom.xml?

Add <maven-jar-plugin.version>3.1.1</maven-jar-plugin.version> in property tag

problem resolve

Uncaught Invariant Violation: Too many re-renders. React limits the number of renders to prevent an infinite loop

I also have the same problem, and the solution is I didn't bind the event in my onClick. so when it renders for the first time and the data is more, which ends up calling the state setter again, which triggers React to call your function again and so on.

export default function Component(props) {

function clickEvent (event, variable){

return (
            onClick={e => clickEvent(e, 10)} // or you can call like this:onClick={() => clickEvent(10)} 

session not created: This version of ChromeDriver only supports Chrome version 74 error with ChromeDriver Chrome using Selenium

I had the very same issue recently. This was my error:

System.InvalidOperationException : session not created: This version of ChromeDriver only supports Chrome version 76 (SessionNotCreated)

This fix worked for me:

  • make sure there are no running chromedriver.exe processes (if needed kill them all e.g. via task manager)
  • go to bin folder and delete chromedriver.exe file from there (in my case it was: [project_folder]\bin\Debug\netcoreapp2.1)

What is useState() in React?

useState is one of build-in react hooks available in 0.16.7 version.

useState should be used only inside functional components. useState is the way if we need an internal state and don't need to implement more complex logic such as lifecycle methods.

const [state, setState] = useState(initialState);

Returns a stateful value, and a function to update it.

During the initial render, the returned state (state) is the same as the value passed as the first argument (initialState).

The setState function is used to update the state. It accepts a new state value and enqueues a re-render of the component.

Please note that useState hook callback for updating the state behaves differently than components this.setState. To show you the difference I prepared two examples.

class UserInfoClass extends React.Component {_x000D_
  state = { firstName: 'John', lastName: 'Doe' };_x000D_
  render() {_x000D_
    return <div>_x000D_
      <p>userInfo: {JSON.stringify(this.state)}</p>_x000D_
      <button onClick={() => this.setState({ _x000D_
        firstName: 'Jason'_x000D_
      })}>Update name to Jason</button>_x000D_
// Please note that new object is created when setUserInfo callback is used_x000D_
function UserInfoFunction() {_x000D_
  const [userInfo, setUserInfo] = React.useState({ _x000D_
    firstName: 'John', lastName: 'Doe',_x000D_
  return (_x000D_
      <p>userInfo: {JSON.stringify(userInfo)}</p>_x000D_
      <button onClick={() => setUserInfo({ firstName: 'Jason' })}>Update name to Jason</button>_x000D_
    <UserInfoClass />_x000D_
    <UserInfoFunction />_x000D_
, document.querySelector('#app'));
<script src="[email protected]/umd/react.development.js"></script>_x000D_
<script src="[email protected]/umd/react-dom.development.js"></script>_x000D_
<div id="app"></div>

New object is created when setUserInfo callback is used. Notice we lost lastName key value. To fixed that we could pass function inside useState.

setUserInfo(prevState => ({ ...prevState, firstName: 'Jason' })

See example:

// Please note that new object is created when setUserInfo callback is used_x000D_
function UserInfoFunction() {_x000D_
  const [userInfo, setUserInfo] = React.useState({ _x000D_
    firstName: 'John', lastName: 'Doe',_x000D_
  return (_x000D_
      <p>userInfo: {JSON.stringify(userInfo)}</p>_x000D_
      <button onClick={() => setUserInfo(prevState => ({_x000D_
        ...prevState, firstName: 'Jason' }))}>_x000D_
        Update name to Jason_x000D_
    <UserInfoFunction />_x000D_
, document.querySelector('#app'));
<script src="[email protected]/umd/react.development.js"></script>_x000D_
<script src="[email protected]/umd/react-dom.development.js"></script>_x000D_
<div id="app"></div>

Unlike the setState method found in class components, useState does not automatically merge update objects. You can replicate this behavior by combining the function updater form with object spread syntax:

setState(prevState => {
  // Object.assign would also work
  return {...prevState, ...updatedValues};

For more about useState see official documentation.

pod has unbound PersistentVolumeClaims

You have to define a PersistentVolume providing disc space to be consumed by the PersistentVolumeClaim.

When using storageClass Kubernetes is going to enable "Dynamic Volume Provisioning" which is not working with the local file system.

To solve your issue:

  • Provide a PersistentVolume fulfilling the constraints of the claim (a size >= 100Mi)
  • Remove the storageClass-line from the PersistentVolumeClaim
  • Remove the StorageClass from your cluster

How do these pieces play together?

At creation of the deployment state-description it is usually known which kind (amount, speed, ...) of storage that application will need.
To make a deployment versatile you'd like to avoid a hard dependency on storage. Kubernetes' volume-abstraction allows you to provide and consume storage in a standardized way.

The PersistentVolumeClaim is used to provide a storage-constraint alongside the deployment of an application.

The PersistentVolume offers cluster-wide volume-instances ready to be consumed ("bound"). One PersistentVolume will be bound to one claim. But since multiple instances of that claim may be run on multiple nodes, that volume may be accessed by multiple nodes.

A PersistentVolume without StorageClass is considered to be static.

"Dynamic Volume Provisioning" alongside with a StorageClass allows the cluster to provision PersistentVolumes on demand. In order to make that work, the given storage provider must support provisioning - this allows the cluster to request the provisioning of a "new" PersistentVolume when an unsatisfied PersistentVolumeClaim pops up.

Example PersistentVolume

In order to find how to specify things you're best advised to take a look at the API for your Kubernetes version, so the following example is build from the API-Reference of K8S 1.17:

apiVersion: v1
kind: PersistentVolume
  name: ckan-pv-home
    type: local
    storage: 100Mi
    path: "/mnt/data/ckan"

The PersistentVolumeSpec allows us to define multiple attributes. I chose a hostPath volume which maps a local directory as content for the volume. The capacity allows the resource scheduler to recognize this volume as applicable in terms of resource needs.

Additional Resources:

Difference between OpenJDK and Adoptium/AdoptOpenJDK

In short:

  • OpenJDK has multiple meanings and can refer to:
    • free and open source implementation of the Java Platform, Standard Edition (Java SE)
    • open source repository — the Java source code aka OpenJDK project
    • prebuilt OpenJDK binaries maintained by Oracle
    • prebuilt OpenJDK binaries maintained by the OpenJDK community
  • AdoptOpenJDK — prebuilt OpenJDK binaries maintained by community (open source licensed)


Prebuilt OpenJDK (or distribution) — binaries, built from, provided as an archive or installer, offered for various platforms, with a possible support contract.

OpenJDK, the source repository (also called OpenJDK project) - is a Mercurial-based open source repository, hosted at The Java source code. The vast majority of Java features (from the VM and the core libraries to the compiler) are based solely on this source repository. Oracle have an alternate fork of this.

OpenJDK, the distribution (see the list of providers below) - is free as in beer and kind of free as in speech, but, you do not get to call Oracle if you have problems with it. There is no support contract. Furthermore, Oracle will only release updates to any OpenJDK (the distribution) version if that release is the most recent Java release, including LTS (long-term support) releases. The day Oracle releases OpenJDK (the distribution) version 12.0, even if there's a security issue with OpenJDK (the distribution) version 11.0, Oracle will not release an update for 11.0. Maintained solely by Oracle.

Some OpenJDK projects - such as OpenJDK 8 and OpenJDK 11 - are maintained by the OpenJDK community and provide releases for some OpenJDK versions for some platforms. The community members have taken responsibility for releasing fixes for security vulnerabilities in these OpenJDK versions.

AdoptOpenJDK, the distribution is very similar to Oracle's OpenJDK distribution (in that it is free, and it is a build produced by compiling the sources from the OpenJDK source repository). AdoptOpenJDK as an entity will not be backporting patches, i.e. there won't be an AdoptOpenJDK 'fork/version' that is materially different from upstream (except for some build script patches for things like Win32 support). Meaning, if members of the community (Oracle or others, but not AdoptOpenJDK as an entity) backport security fixes to updates of OpenJDK LTS versions, then AdoptOpenJDK will provide builds for those. Maintained by OpenJDK community.

OracleJDK - is yet another distribution. Starting with JDK12 there will be no free version of OracleJDK. Oracle's JDK distribution offering is intended for commercial support. You pay for this, but then you get to rely on Oracle for support. Unlike Oracle's OpenJDK offering, OracleJDK comes with longer support for LTS versions. As a developer you can get a free license for personal/development use only of this particular JDK, but that's mostly a red herring, as 'just the binary' is basically the same as the OpenJDK binary. I guess it means you can download security-patched versions of LTS JDKs from Oracle's websites as long as you promise not to use them commercially.

Note. It may be best to call the OpenJDK builds by Oracle the "Oracle OpenJDK builds".

Donald Smith, Java product manager at Oracle writes:

Ideally, we would simply refer to all Oracle JDK builds as the "Oracle JDK", either under the GPL or the commercial license, depending on your situation. However, for historical reasons, while the small remaining differences exist, we will refer to them separately as Oracle’s OpenJDK builds and the Oracle JDK.

OpenJDK Providers and Comparison

|     Provider      | Free Builds | Free Binary   | Extended | Commercial | Permissive |
|                   | from Source | Distributions | Updates  | Support    | License    |
| AdoptOpenJDK      |    Yes      |    Yes        |   Yes    |   No       |   Yes      |
| Amazon – Corretto |    Yes      |    Yes        |   Yes    |   No       |   Yes      |
| Azul Zulu         |    No       |    Yes        |   Yes    |   Yes      |   Yes      |
| BellSoft Liberica |    No       |    Yes        |   Yes    |   Yes      |   Yes      |
| IBM               |    No       |    No         |   Yes    |   Yes      |   Yes      |
| jClarity          |    No       |    No         |   Yes    |   Yes      |   Yes      |
| OpenJDK           |    Yes      |    Yes        |   Yes    |   No       |   Yes      |
| Oracle JDK        |    No       |    Yes        |   No**   |   Yes      |   No       |
| Oracle OpenJDK    |    Yes      |    Yes        |   No     |   No       |   Yes      |
| ojdkbuild         |    Yes      |    Yes        |   No     |   No       |   Yes      |
| RedHat            |    Yes      |    Yes        |   Yes    |   Yes      |   Yes      |
| SapMachine        |    Yes      |    Yes        |   Yes    |   Yes      |   Yes      |

Free Builds from Source - the distribution source code is publicly available and one can assemble its own build

Free Binary Distributions - the distribution binaries are publicly available for download and usage

Extended Updates - aka LTS (long-term support) - Public Updates beyond the 6-month release lifecycle

Commercial Support - some providers offer extended updates and customer support to paying customers, e.g. Oracle JDK (support details)

Permissive License - the distribution license is non-protective, e.g. Apache 2.0

Which Java Distribution Should I Use?

In the Sun/Oracle days, it was usually Sun/Oracle producing the proprietary downstream JDK distributions based on OpenJDK sources. Recently, Oracle had decided to do their own proprietary builds only with the commercial support attached. They graciously publish the OpenJDK builds as well on their site.

What is happening starting JDK 11 is the shift from single-vendor (Oracle) mindset to the mindset where you select a provider that gives you a distribution for the product, under the conditions you like: platforms they build for, frequency and promptness of releases, how support is structured, etc. If you don't trust any of existing vendors, you can even build OpenJDK yourself.

Each build of OpenJDK is usually made from the same original upstream source repository (OpenJDK “the project”). However each build is quite unique - $free or commercial, branded or unbranded, pure or bundled (e.g., BellSoft Liberica JDK offers bundled JavaFX, which was removed from Oracle builds starting JDK 11).

If no environment (e.g., Linux) and/or license requirement defines specific distribution and if you want the most standard JDK build, then probably the best option is to use OpenJDK by Oracle or AdoptOpenJDK.

Additional information

Time to look beyond Oracle's JDK by Stephen Colebourne

Java Is Still Free by Java Champions community (published on September 17, 2018)

Java is Still Free 2.0.0 by Java Champions community (published on March 3, 2019)

Aleksey Shipilev about JDK updates interview by Opsian (published on June 27, 2019)

ERROR Error: Uncaught (in promise), Cannot match any routes. URL Segment

As the error says your router link should match the existing routes configured

It should be just routerLink="/about"

Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve

As @Ebin Joy said, If your gradle file get corrupted then there is one simple solution for that. Manually give the proxy details like shown in image. then you're good to go. This solution only works if you using any closed networks like office network etc.

enter image description here

How to uninstall Eclipse?

There is no automated uninstaller.

You have to remove Eclipse manually. At least Eclipse does not write anything in the system registry, so deleting some directories and files is enough.

Note: I use Unix style paths in this answer but the locations should be the same on Windows or Unix systems, so ~ refers to the user home directory even on Windows.

Why is there no uninstaller?

According to this discussion about uninstalling Eclipse, the reasoning for not providing an uninstaller is that the Eclipse installer is supposed to just automate a few tasks that in the past had to be done manually (like downloading and extracting Eclipse and adding shortcuts), so they also can be undone manually. There is no entry in "Programs and Features" because the installer does not register anything in the system registry.

How to quickly uninstall Eclipse

Just delete the Eclipse directory and any desktop and start menu shortcuts and be done with it, if you don't mind a few leftover files.

In my opinion this is generally enough and I would stop here, because multiple Eclipse installations can share some files and you don't accidentally want to delete those shared files. You also keep all your projects.

How to completely uninstall Eclipse

If you really want to remove Eclipse without leaving any traces, you have to manually delete

  • all desktop and start menu shortcuts
  • the installation directory (e.g. ~/eclipse/photon/)
  • the p2 bundle pool (which is often shared with other eclipse installations)

The installer has a "Bundle Pools" menu entry which lists the locations of all bundle pools. If you have other Eclipse installations on your system you can use the "Cleanup Agent" to clean up unused bundles. If you don't have any other Eclipse installations you can delete the whole bundle pool directory instead (by default ~/p2/).

If you want to completely remove the Eclipse installer too, delete the installer's executable and the ~/.eclipse/ directory.

Depending on what kind of work you did with Eclipse, there can be more directories that you may want to delete. If you used Maven, then ~/.m2/ contains the Maven cache and settings (shared with Maven CLI and other IDEs). If you develop Eclipse plugins, then there might be JUnit workspaces from test runs, next to you Eclipse workspace. Likewise other build tools and development environments used in Eclipse could have created similar directories.

How to delete all projects

If you want to delete your projects and workspace metadata, you have to delete your workspace(s). The default workspace location is ´~/workspace/´. You can also search for the .metadata directory to get all Eclipse workspaces on your machine.

If you are working with Git projects, these are generally not saved in the workspace but in the ~/git/ directory.

How to resolve Unable to load authentication plugin 'caching_sha2_password' issue

As Mentioned in above repilies:

Starting with MySQL 8.0.4, the MySQL team changed the default authentication plugin for MySQL server from mysql_native_password to caching_sha2_password.

So there are three ways to resolve this issue:

 1. drop USER 'user_name'@'localhost';
    flush privileges;
    CREATE USER 'user_name'@'localhost' IDENTIFIED BY 'user_name';
    GRANT ALL PRIVILEGES ON * . * TO 'user_name'@'localhost';
    ALTER USER 'user_name'@'localhost' IDENTIFIED WITH mysql_native_password BY 

 2. drop USER 'user_name'@'localhost';
    flush privileges;
    CREATE USER 'user_name'@'localhost' IDENTIFIED WITH mysql_native_password BY 'user_name';
GRANT ALL PRIVILEGES ON * . * TO 'user_name'@'localhost'

 3. If the user is already created, the use the following command:

    ALTER USER 'user_name'@'localhost' IDENTIFIED WITH mysql_native_password BY 

Importing json file in TypeScript

The import form and the module declaration need to agree about the shape of the module, about what it exports.

When you write (a suboptimal practice for importing JSON since TypeScript 2.9 when targeting compatible module formatssee note)

declare module "*.json" {
  const value: any;
  export default value;

You are stating that all modules that have a specifier ending in .json have a single export named default.

There are several ways you can correctly consume such a module including

import a from "a.json";


import * as a from "a.json";


import {default as a} from "a.json";


import a = require("a.json");

The first form is the best and the syntactic sugar it leverages is the very reason JavaScript has default exports.

However I mentioned the other forms to give you a hint about what's going wrong. Pay special attention to the last one. require gives you an object representing the module itself and not its exported bindings.

So why the error? Because you wrote

import a = require("a.json");

And yet there is no export named primaryMain declared by your "*.json".

All of this assumes that your module loader is providing the JSON as the default export as suggested by your original declaration.

Note: Since TypeScript 2.9, you can use the --resolveJsonModule compiler flag to have TypeScript analyze imported .json files and provide correct information regarding their shape obviating the need for a wildcard module declaration and validating the presence of the file. This is not supported for certain target module formats.

Uncaught (in promise): Error: StaticInjectorError(AppModule)[options]

In my case, the error was in using angular2-notifications 0.9.8 instead of 0.9.7

After Spring Boot 2.0 migration: jdbcUrl is required with driverClassName

Others have answered so I'll add my 2-cents.

You can either use autoconfiguration (i.e. don't use a @Configuration to create a datasource) or java configuration.


define your datasource type then set the type properties. E.g.


Java configuration:

Choose a prefix and define your data source


Create your datasource bean:

@Bean(name = { "dataSource", "mysystemDataSource" })
@ConfigurationProperties(prefix = "spring.mysystem.datasource")
public DataSource dataSource() {
    return DataSourceBuilder.create().build();

You can leave the datasource type out, but then you risk spring guessing what datasource type to use.

Issue in installing php7.2-mcrypt

As an alternative, you can install 7.1 version of mcrypt and create a symbolic link to it:

Install php7.1-mcrypt:

sudo apt install php7.1-mcrypt

Create a symbolic link:

sudo ln -s /etc/php/7.1/mods-available/mcrypt.ini /etc/php/7.2/mods-available

After enabling mcrypt by sudo phpenmod mcrypt, it gets available.

'mat-form-field' is not a known element - Angular 5 & Material2

I had this problem too. It turned out I forgot to include one of the components in app.module.ts

The type WebMvcConfigurerAdapter is deprecated

Use org.springframework.web.servlet.config.annotation.WebMvcConfigurer

With Spring Boot 2.1.4.RELEASE (Spring Framework 5.1.6.RELEASE), do like this

package vn.bkit;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter; // Deprecated.
import org.springframework.web.servlet.view.InternalResourceViewResolver;

public class MvcConfiguration implements WebMvcConfigurer {

    public ViewResolver getViewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        return resolver;

    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {


Class has been compiled by a more recent version of the Java Environment

Go to Project section, click on properties > then to Java compiler > check compiler compliance level is 1.8 , or there should be no yellow warning at bottom

Could not resolve in Android Studio new project

This work for me. In the android\app\build.gradle file you need to specify the following

compileSdkVersion 26
buildToolsVersion "26.0.1"

and then find this

compile ""

and make sure it says

compile ""

Where to declare variable in react js

Using ES6 syntax in React does not bind this to user-defined functions however it will bind this to the component lifecycle methods.

So the function that you declared will not have the same context as the class and trying to access this will not give you what you are expecting.

For getting the context of class you have to bind the context of class to the function or use arrow functions.

Method 1 to bind the context:

class MyContainer extends Component {

    constructor(props) {
        this.onMove = this.onMove.bind(this);
        this.testVarible= "this is a test";

    onMove() {

Method 2 to bind the context:

class MyContainer extends Component {

    constructor(props) {
        this.testVarible= "this is a test";

    onMove = () => {

Method 2 is my preferred way but you are free to choose your own.

Update: You can also create the properties on class without constructor:

class MyContainer extends Component {

    testVarible= "this is a test";

    onMove = () => {

Note If you want to update the view as well, you should use state and setState method when you set or change the value.


class MyContainer extends Component {

    state = { testVarible: "this is a test" };

    onMove = () => {
        this.setState({ testVarible: "new value" });

NullInjectorError: No provider for AngularFirestore

Adding AngularFirestoreModule.enablePersistence() in import section resolved my issue:

imports: [
    BrowserModule, AngularFireModule, 

No provider for HttpClient

I was facing the same issue, the funny thing was I had two projects opened on simultaneously, I have changed the wrong app.modules.ts files.

First, check that.

After that change add the following code to the app.module.ts file

import { HttpClientModule } from '@angular/common/http';

After that add the following to the imports array in the app.module.ts file

  imports: [

Now you should be ok!

Unable to resolve dependency for ':app@debug/compileClasspath': Could not resolve

For other people where the accepted answer does not solve this issue...

As of September 2018, AndroidX has replaced the Android Support Libraries, which includes the appcompat-v7 library.

'' becomes 'androidx.appcompat:appcompat:1.0.0'

'' becomes ''

References: List of Support Libraries to AndroidX mappings

Angular 4: no component factory found,did you add it to @NgModule.entryComponents?

  1. entryComponents is vital. Above answers on this are correct.


  1. If you're providing a service that opens the modal (a common pattern) and your module that defines the dialog component is not loaded in AppModule, you need to change providedIn: 'root' to providedIn: MyModule. As general good practice you should just use the providedIn: SomeModule for all dialog services that are in modules.

Android studio 3.0: Unable to resolve dependency for :app@dexOptions/compileClasspath': Could not resolve project :animators

I tried everything from unchecking offline work to matchingFallbacks. But nothing worked.

Then, in dependencies of app.gradle,

instead of

implementation project(':lib-name')

I used,

implementation project(path:':lib-name', configuration: 'default')

Eg: implementation project(path:':myService', configuration: 'default')

And it worked like a charm. :)

I was adding a dependency module with service and am not making a library as its a part of AOSP project.

Just in case, it helps someone.

Is there a way to remove unused imports and declarations from Angular 2+?

To be able to detect unused imports, code or variables, make sure you have this options in tsconfig.json file

"compilerOptions": {
    "noUnusedLocals": true,
    "noUnusedParameters": true

have the typescript compiler installed, ifnot install it with:

npm install -g typescript

and the tslint extension installed in Vcode, this worked for me, but after enabling I notice an increase amount of CPU usage, specially on big projects.

I would also recomend using typescript hero extension for organizing your imports.

Eclipse No tests found using JUnit 5 caused by NoClassDefFoundError for LauncherFactory

you should change

public static void testmethod(){}


public void testmethod(){}

the @Test is unsupport static method

Is it safe to clean docker/overlay2/

I recently had a similar issue, overlay2 grew bigger and bigger, But I couldn’t figure out what consumed the bulk of the space.

df showed me that overlay2 was about 24GB in size.

With du I tried to figure out what occupied the space… and failed.

The difference came from the fact that deleted files (mostly log files in my case) where still being used by a process (Docker). Thus the file doesn’t show up with du but the space it occupies will show with df.

A reboot of the host machine helped. Restarting the docker container would probably have helped already… This article on helped me to figure that out.

Please add a @Pipe/@Directive/@Component annotation. Error

If you are exporting another class in that module, make sure that it is not in between @Component and your ClassComponent. For example:

@Component({ ... })

export class ExampleClass{}

export class ComponentClass{}  --> this will give this error.


export class ExampleClass{}

@Component ({ ... })

export class ComponentClass{}

How to downgrade Java from 9 to 8 on a MACOS. Eclipse is not running with Java 9

If you have multiple Java versions installed on your Mac, here's a quick way to switch the default version using Terminal. In this example, I am going to switch Java 10 to Java 8.

$ java -version
java version "10.0.1" 2018-04-17
Java(TM) SE Runtime Environment 18.3 (build 10.0.1+10)
Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10.0.1+10, mixed mode)

$ /usr/libexec/java_home -V
Matching Java Virtual Machines (2):
    10.0.1, x86_64: "Java SE 10.0.1"    /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
    1.8.0_171, x86_64:  "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home


Then, in your .bash_profile add the following.

# Java 8
export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home

Now if you try java -version again, you should see the version you want.

$ java -version
java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)

Property 'json' does not exist on type 'Object'

The other way to tackle it is to use this code snippet:


This feels so wrong but it works

How to get param from url in angular 4?

You can try this:

this.activatedRoute.paramMap.subscribe(x => {
    let id = x.get('id');

VSCode cannot find module '@angular/core' or any other modules

This worked for me.

 npm install --save-dev @angular-devkit/build-angular

"The POM for ... is missing, no dependency information available" even though it exists in Maven Repository

You will need to add external Repository to your pom, since this is using Mulsoft-Release repository not Maven Central

            <name>MuleSoft Repository</name>


Apache Maven - Setting up Multiple Repositories

Get current url in Angular

You can make use of location service available in @angular/common and via this below code you can get the location or current URL

import { Component, OnInit } from '@angular/core';
import { Location } from '@angular/common';
import { Router } from '@angular/router';

  selector: 'app-top-nav',
  templateUrl: './top-nav.component.html',
  styleUrls: ['./top-nav.component.scss']
export class TopNavComponent implements OnInit {

  route: string;

  constructor(location: Location, router: Router) { => {
      if(location.path() != ''){
        this.route = location.path();
      } else {
        this.route = 'Home'

  ngOnInit() {


here is the reference link from where I have copied thing to get location for my project.

element not interactable exception in selenium web automation

you may also try full xpath, I had a similar issue where I had to click on an element which has a property javascript onclick function. the full xpath method worked and no interactable exception was thrown.

Specifying onClick event type with Typescript and React.Konva

React.MouseEvent works for me:

private onClick = (e: React.MouseEvent<HTMLInputElement>) => {
  let button = as HTMLInputElement;

Uncaught Error: Unexpected module 'FormsModule' declared by the module 'AppModule'. Please add a @Pipe/@Directive/@Component annotation

Add FormsModule in Imports Array.

declarations: [
imports: [
providers: [],
bootstrap: [AppComponent]

Or this can be done without using [(ngModel)] by using

<input [value]='' (input)='$' placeholder="name">

instead of

<input [(ngModel)]="" placeholder="Name">

Selenium Web Driver & Java. Element is not clickable at point (x, y). Other element would receive the click

In case you need to use it with Javascript

We can use arguments[0].click() to simulate click operation.

var element = element(by.linkText('webdriverjs'));

Component is not part of any NgModule or the module has not been imported into your module

I ran into the same issue. I had created another component with the same name under a different folder. so in my app module I had to import both components but with a trick

import {DuplicateComponent as AdminDuplicateComponent} from '/the/path/to/the/component';

Then in declarations I could add AdminDuplicateComponent instead.

Just thought that I would leave that there for future reference.

Angular CLI - Please add a @NgModule annotation when using latest

In my case, I created a new ChildComponent in Parentcomponent whereas both in the same module but Parent is registered in a shared module so I created ChildComponent using CLI which registered Child in the current module but my parent was registered in the shared module.

So register the ChildComponent in Shared Module manually.

Angular 4 Pipe Filter

The transform method signature changed somewhere in an RC of Angular 2. Try something more like this:

export class FilterPipe implements PipeTransform {
    transform(items: any[], filterBy: string): any {
        return items.filter(item => !== -1);

And if you want to handle nulls and make the filter case insensitive, you may want to do something more like the one I have here:

export class ProductFilterPipe implements PipeTransform {

    transform(value: IProduct[], filterBy: string): IProduct[] {
        filterBy = filterBy ? filterBy.toLocaleLowerCase() : null;
        return filterBy ? value.filter((product: IProduct) =>
            product.productName.toLocaleLowerCase().indexOf(filterBy) !== -1) : value;

And NOTE: Sorting and filtering in pipes is a big issue with performance and they are NOT recommended. See the docs here for more info:

'router-outlet' is not a known element

Here is the Quick and Simple Solution if anyone is getting the error:

"'router-outlet' is not a known element" in angular project,


Just go to the "app.module.ts" file & add the following Line:

import { AppRoutingModule } from './app-routing.module';

And also 'AppRoutingModule' in imports.

Angular 2 'component' is not a known element

I know this is a long resolved problem, but in my case I had a different solution. It was actually a mistake I made that maybe you made as well and didn't fully notice. My mistake was that I accidentally placed a Module e.g., MatChipsModule, MatAutoCompleteModule, on the declarations section; the section that is composed only by components e.g., MainComponent, AboutComponent. This made all my other import unrecognizable.

More than one file was found with OS independent path 'META-INF/LICENSE'

I faced this issue, first with some native libraries (.so files) and then with java/kotlin files. Turned out I was including a library from source as well as referencing artifactory through a transitive dependency. Check your dependency tree to see if there are any redundant entries. Use ./gradlew :app:dependencies to get the dependency tree. Replace "app" with your module name if the main module name is different.

When to use 'raise NotImplementedError'?

As Uriel says, it is meant for a method in an abstract class that should be implemented in child class, but can be used to indicate a TODO as well.

There is an alternative for the first use case: Abstract Base Classes. Those help creating abstract classes.

Here's a Python 3 example:

class C(abc.ABC):
    def my_abstract_method(self, ...):

When instantiating C, you'll get an error because my_abstract_method is abstract. You need to implement it in a child class.

TypeError: Can't instantiate abstract class C with abstract methods my_abstract_method

Subclass C and implement my_abstract_method.

class D(C):
    def my_abstract_method(self, ...):

Now you can instantiate D.

C.my_abstract_method does not have to be empty. It can be called from D using super().

An advantage of this over NotImplementedError is that you get an explicit Exception at instantiation time, not at method call time.

Val and Var in Kotlin

variables defined with var are mutable(Read and Write)

variables defined with val are immutable(Read only)

Kotlin can remove findViewById and reduce code for setOnClickListener in android studio. For full reference: Kotlin awesome features

value of mutable variables can be changed at anytime, while you can not change value of immutable variables.

where should I use var and where val ?

use var where value is changing frequently. For example while getting location of android device

var integerVariable : Int? = null

use val where there is no change in value in whole class. For example you want set textview or button's text programmatically.

val stringVariables : String = "Button's Constant or final Text"

Android Room - simple select query - Cannot access database on the main thread

In my opinion the right thing to do is to delegate the query to an IO thread using RxJava.

I have an example of a solution to an equivalent problem I've just encountered.

((ProgressBar) view.findViewById(;//Always good to set some good feedback
        Completable.fromAction(() -> {
            //Creating view model requires DB access
            homeViewModel = new ViewModelProvider(this, factory).get(HomeViewModel.class);
        }).subscribeOn( DB access executes on a non-main-thread thread
        .observeOn(AndroidSchedulers.mainThread())//Upon completion of the DB-involved execution, the continuation runs on the main thread
                () ->
                    mAdapter = new MyAdapter(homeViewModel.getExams());
                    ((ProgressBar) view.findViewById(;
                error -> error.printStackTrace()

And if we want to generalize the solution:

((ProgressBar) view.findViewById(;//Always good to set some good feedback
        Completable.fromAction(() -> {
        }).subscribeOn( long task executes on a non-main-thread thread
        .observeOn(AndroidSchedulers.mainThread())//Upon completion of the DB-involved execution, the continuation runs on the main thread
                () ->
                error -> error.printStackTrace()

Load json from local file with http.get() in angular 2


I created a new component called test in this folder:

enter image description here

I also created a mock called test.json in the assests folder created by angular cli (important):

enter image description here

This mock looks like this:

            "id": 1,
            "name": "Item 1"
            "id": 2,
            "name": "Item 2"
            "id": 3,
            "name": "Item 3"

In the controller of my component test import follow rxjs like this

import 'rxjs/add/operator/map'

This is important, because you have to map your response from the http get call, so you get a json and can loop it in your ngFor. Here is my code how I load the mock data. I used http get and called my path to the mock with this path this.http.get("/assets/mock/test/test.json"). After this i map the response and subscribe it. Then I assign it to my variable items and loop it with ngFor in my template. I also export the type. Here is my whole controller code:

import { Component, OnInit } from "@angular/core";
import { Http, Response } from "@angular/http";
import 'rxjs/add/operator/map'

export type Item = { id: number, name: string };

  selector: "test",
  templateUrl: "./test.component.html",
  styleUrls: ["./test.component.scss"]
export class TestComponent implements OnInit {
  items: Array<Item>;

  constructor(private http: Http) {}

  ngOnInit() {
      .map(data => data.json() as Array<Item>)
      .subscribe(data => {
        this.items = data;

And my loop in it's template:

<div *ngFor="let item of items">

It works as expected! I can now add more mock files in the assests folder and just change the path to get it as json. Notice that you have also to import the HTTP and Response in your controller. The same in you app.module.ts (main) like this:

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { HttpModule, JsonpModule } from '@angular/http';

import { AppComponent } from './app.component';
import { TestComponent } from './components/molecules/test/test.component';

  declarations: [
  imports: [
  providers: [],
  bootstrap: [AppComponent]
export class AppModule { }

How to print a Groovy variable in Jenkins?

You shouldn't use ${varName} when you're outside of strings, you should just use varName. Inside strings you use it like this; echo "this is a string ${someVariable}";. Infact you can place an general java expression inside of ${...}; echo "this is a string ${func(arg1, arg2)}.

Error:Execution failed for task ':app:compileDebugKotlin'. > Compilation error. See log for more details

I faced the similar problem in no reason, i think it was caused by IDE(android studio). I have tried all of above solutions but not worked. Finally, in my own situation, i solved this problem by the following actions: - Close the current project and remove it from the list of projects in android studio ,and reopen it by Open an existing Android Studio project, then it may be worked. I hope that my experience will be useful for you.

Linker Command failed with exit code 1 (use -v to see invocation), Xcode 8, Swift 3

Ok, I had the same problem just today and started googling it, when I came across this thread. I haven't finished reading the question when the answer struck my mind: I declared a class with an empty constructor

class MyClass{

    void func_one(){
    // code

    void func_two(){
    // code

        cout << "Deleting object" << endl;

Then I thought why not terminating (not sure if I'm correct with word selection here, but who cares) the constructor of my class with curly braces ({}). So I did:

class MyClass{

    void func_one(){
    // code

    void func_two(){
    // code

        cout << "Deleting object" << endl;

The problem eliminated, my code started working perfectly.

I know, the good practice is to investigate the issue and find the real cause, but this worked for me.

How to import functions from different js file in a Vue+webpack+vue-loader project

I like the answer of Anacrust, though, by the fact "console.log" is executed twice, I would like to do a small update for src/mylib.js:

let test = {
  foo () { return 'foo' },
  bar () { return 'bar' },
  baz () { return 'baz' }

export default test

All other code remains the same...

Component is part of the declaration of 2 modules

To surpass this error , you should start by removing all the imports of app.module.ts and have something like this :

            import { BrowserModule } from '@angular/platform-browser';
            import { HttpClientModule } from '@angular/common/http';
            import { ErrorHandler, NgModule } from '@angular/core';
            import { IonicApp, IonicErrorHandler, IonicModule } from 'ionic-angular';
            import { SplashScreen } from '@ionic-native/splash-screen';
            import { StatusBar } from '@ionic-native/status-bar';

            import { MyApp } from './app.component';

              declarations: [
              imports: [
              bootstrap: [IonicApp],
              entryComponents: [
              providers: [
                {provide: ErrorHandler, useClass: IonicErrorHandler}
            export class AppModule {}

Next edit your pages module , like this :

            import { NgModule } from '@angular/core';
            import { IonicPageModule } from 'ionic-angular';
            import { HomePage } from './home';

              declarations: [
              imports: [
              entryComponents: [HomePage]
            export class HomePageModule {}

Then add annotation of IonicPage before component annotation of all the pages :

import { IonicPage } from 'ionic-angular';

  selector: 'page-home',
  templateUrl: 'home.html'

Then edit your rootPage type to be string and remove the imports of pages (if there is any in your app component )

rootPage: string = 'HomePage';

Then the navigation function should be like this :

* Allow navigation to the HomePage for creating a new entry
* @public
* @method viewHome
* @return {None}
 viewHome() : void

You can find the source of this solution here : Component is part of the declaration of 2 modules

Jenkins pipeline if else not working

your first try is using declarative pipelines, and the second working one is using scripted pipelines. you need to enclose steps in a steps declaration, and you can't use if as a top-level step in declarative, so you need to wrap it in a script step. here's a working declarative version:

pipeline {
    agent any

    stages {
        stage('test') {
            steps {
                sh 'echo hello'
        stage('test1') {
            steps {
                sh 'echo $TEST'
        stage('test3') {
            steps {
                script {
                    if (env.BRANCH_NAME == 'master') {
                        echo 'I only execute on the master branch'
                    } else {
                        echo 'I execute elsewhere'

you can simplify this and potentially avoid the if statement (as long as you don't need the else) by using "when". See "when directive" at you can also validate jenkinsfiles using the jenkins rest api. it's super sweet. have fun with declarative pipelines in jenkins!

Visual Studio Code pylint: Unable to import 'protorpc'

I got the same error on my vscode where I had a library installed and the code working when running from the terminal, but for some reason, the vscode pylint was not able to pick the installed package returning the infamous error:

Unable to import 'someLibrary.someModule' pylint(import-error)

The problem might arise due to the multiple Python installations. Basically you have installed a library/package on one, and vscode pylint is installed and running from another installation. For example, on macOS and many Linux distros, there are by default Python2 installed and when you install Python3 this might cause confusion. Also on windows the Chocolatey package manager might cause some mess and you end up with multiple Python installations. To figure it out if you are on a *nix machine (i.e., macOS, GNU/Linux, BSD...), use the which command, and if you are on Windows, use the where command to find the installed Python interpreters. For example, on *nix machines:

which python3

and on Windows

where python

then you may want to uninstall the ones you don't want. and the one you want to use check if the package causing above issue is installed by

python -c "import someLibrary"

if you get an error then you should install it by for example pip:

pip install someLibrary

then on vscode press ??P if you are on a mac and CtrlShiftP on other operating systems. Then type-select the >python: Select Interpreter option and select the one you know have the library installed. At this moment vscode might asks you to install pyling again, which you just go on with.

Prevent content from expanding grid items

The previous answer is pretty good, but I also wanted to mention that there is a fixed layout equivalent for grids, you just need to write minmax(0, 1fr) instead of 1fr as your track size.

Angular2 : Can't bind to 'formGroup' since it isn't a known property of 'form'

For those still struggling with the error, make sure that you also import ReactiveFormsModule in your component 's module.ts file

meaning that you will import your ReactiveFormsModule in your app.module.ts and also in your mycomponent.module.ts file

How to use Redirect in the new react-router-dom of Reactjs

The problem I run into is I have an existing IIS machine. I then deploy a static React app to it. When you use router, the URL that displays is actually virtual, not real. If you hit F5 it goes to IIS, not index.js, and your return will be 404 file not found. How I resolved it was simple. I have a public folder in my react app. In that public folder I created the same folder name as the virtual routing. In this folder, I have an index.html with the following code:

    localStorage.setItem("redirect", "/ansible/");
    location.href = "/";

Now what this does is for this session, I'm adding the "routing" path I want it to go. Then inside my App.js I do this (Note ... is other code but too much to put here for a demo):

import React, { Component } from "react";
import { Route, Link } from "react-router-dom";
import { BrowserRouter as Router } from "react-router-dom";
import { Redirect } from 'react-router';
import Ansible from "./Development/Ansible";
import Code from "./Development/Code";
import Wood from "./WoodWorking";
import "./App.css";

class App extends Component {
  render() {
    const redirect = localStorage.getItem("redirect");

    if(redirect) {

    return (
        {redirect ?<Redirect to={redirect}/> : ""}
        <div className="App">
          <Link to="/">
          <Link to="/dev">
          <Link to="/wood">
            <li>Wood Working</li>
            render={(props) => (
              <Home {...props} />
            render={(props) => (
              <Code {...props} />
            render={(props) => (
              <Wood {...props} />
            render={(props) => (
              <Ansible {...props} checked={this.state.checked} />

export default App;

Actual usage:

typescript: error TS2693: 'Promise' only refers to a type, but is being used as a value here

Here is my tip. Tested with vscode 1.21.1 (on MAC)

Put below config to tsconfig.json

"lib": [

into compilerOptions

Restart IDE (this action is required :D )

Cannot find name 'require' after upgrading to Angular4

As for me, using VSCode and Angular 5, only had to add "node" to types in Save, and restart the server.

    "compilerOptions": {_x000D_
    "types": [_x000D_

One curious thing, is that this problem "cannot find require (", does not happen when excuting with ts-node

Spring Boot application in eclipse, the Tomcat connector configured to listen on port XXXX failed to start

In your windows os follow the following steps:

1)search services 2)Find Apache tomcat 3)Right-click on it and select end 4)Run your spring boot application again it will work

Make Axios send cookies in its requests automatically


{ withCredentials: true } or axios.defaults.withCredentials = true

From the axios documentation

withCredentials: false, // default

withCredentials indicates whether or not cross-site Access-Control requests should be made using credentials

If you pass { withCredentials: true } with your request it should work.

A better way would be setting withCredentials as true in axios.defaults

axios.defaults.withCredentials = true

In Angular, What is 'pathmatch: full' and what effect does it have?

      { path: 'welcome', component: WelcomeComponent },
      { path: '', redirectTo: 'welcome', pathMatch: 'full' },
      { path: '**', component: 'pageNotFoundComponent' }

Case 1 pathMatch:'full': In this case, when app is launched on localhost:4200 (or some server) the default page will be welcome screen, since the url will be https://localhost:4200/

If https://localhost:4200/gibberish this will redirect to pageNotFound screen because of path:'**' wildcard

Case 2 pathMatch:'prefix':

If the routes have { path: '', redirectTo: 'welcome', pathMatch: 'prefix' }, now this will never reach the wildcard route since every url would match path:'' defined.

How to resolve Unneccessary Stubbing exception

I had UnnecessaryStubbingException when I tried to use the when methods on a Spy object. Mockito.lenient() silenced the exception but the test results were not correct.

In case of Spy objects, one has to call the methods directly.

class ArithmTest {

    private Arithm arithm;

    void testAddition() {

        int res = arithm.add(2, 5);

        // doReturn(7).when(arithm).add(2, 5);
        assertEquals(res, 7);

[Vue warn]: Property or method is not defined on the instance but referenced during render

It is most likely a spelling error of reserved vuejs variables. I got here because I misspelled computed: and vuejs would not recognize my computed property variables. So if you have an error like this, check your spelling first!

No provider for Router?

Babar Bilal's answer likely worked perfectly for earlier Angular 2 alpha/beta releases. However, anyone solving this problem with Angular release v4+ may want to try the following change to his answer instead (wrapping the single route in the required array):

RouterModule.forRoot([{ path: "", component: LoginComponent}])

Visual Studio 2017: Display method references

For anyone who looks at this today after 2 years, Visual Studio 2019 (Community edition as well) shows the references

Angular cli generate a service and include the provider in one step

Angular 6+ Singleton Services

The recommended approach for a singleton service for Angular 6 and beyond is :

import { Injectable } from '@angular/core';

  providedIn: 'root',
export class UserService {

In fact the CLI --module switch doesn't even exist any more for registering a service at the app level because it doesn't need to modify app.module.ts anymore.

This will create the above code, without needing to specify a module.

ng g s services/user

So if you don't want your service to be a singleton you must remove the providedIn code yourself - and then add it manually to providers for a component or lazy loaded module. Doesn't look like there is currently a switch to not generate the providedIn: 'root' part so you need to manually remove it.

PHP: cannot declare class because the name is already in use

You should use require_once and include_once. Inside parent.php use

include_once 'database.php';

And inside child1.php and child2.php use

include_once 'parent.php';

REACT - toggle class onclick

React has a concept of components state, so if you want to Toggle, use setState:

  1. App.js
import React from 'react';

import TestState from './components/TestState';

class App extends React.Component {
  render() {
    return (
      <div className="App">
        <h1>React State Example</h1>

export default App;
  1. components/TestState.js
import React from 'react';

class TestState extends React.Component

        this.state = {
            message: 'Please subscribe',
            status: "Subscribe"

        if (this.state.status === 'Subscribe')
            this.setState({message : 'Thank You For Scubscribing.', status: 'Unsubscribe'})
            this.setState({ message: 'Please subscribe', status: 'Subscribe' })
        return (
        <button onClick={()=> this.changeMessage() } >{this.state.status}</button>

export default TestState;
  1. Output

enter image description here

Error: Could not find gradle wrapper within Android SDK. Might need to update your Android SDK - Android

After trying everything here twice in different order, I reinstalled everything and before doing cordova platform add android I went to templates/gradle and ran gradlew.bat. After this completed, I was able to add the android platform without any problem.

React: trigger onChange if input value is changing by state?

I think you should change that like so:

<input value={this.state.value} onChange={(e) => {this.handleChange(e)}}/>

That is in principle the same as onClick={this.handleClick.bind(this)} as you did on the button.

So if you want to call handleChange() when the button is clicked, than:

<button onClick={this.handleChange.bind(this)}>Change Input</button>


handleClick () {
  this.setState({value: 'another random text'});

How to set and reference a variable in a Jenkinsfile

The error is due to that you're only allowed to use pipeline steps inside the steps directive. One workaround that I know is to use the script step and wrap arbitrary pipeline script inside of it and save the result in the environment variable so that it can be used later.

So in your case:

pipeline {
    agent any
    stages {
        stage("foo") {
            steps {
                script {
                    env.FILENAME = readFile 'output.txt'
                echo "${env.FILENAME}"

Maven build Compilation error : Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project Maven

I am not able to run my own build on the other suggestions here. I even tried different versions of maven-compiler-plugin: 3.1, 3.7.0, etc.

I made it work adding this:


I tried this approach because it seems like the /src/test/java directory is considered a java class that is why it is compiled the same time as /src/test/java. So my hunch were right in my case.

Maybe it is to others too, so just try this one.

Jenkins: Can comments be added to a Jenkinsfile?

Comments work fine in any of the usual Java/Groovy forms, but you can't currently use groovydoc to process your Jenkinsfile (s).

First, groovydoc chokes on files without extensions with the wonderful error

    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(
    at java.lang.reflect.Method.invoke(
Caused by: java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(
    at$ Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(
    ... 6 more

... and second, as far as I can tell Javadoc-style commments at the start of a groovy script are ignored. So even if you copy/rename your Jenkinsfile to Jenkinsfile.groovy, you won't get much useful output.

I want to be able to use a

 * Document my Jenkinsfile's overall purpose here

comment at the start of my Jenkinsfile. No such luck (yet).

groovydoc will process classes and methods defined in your Jenkinsfile if you pass -private to the command, though.

How to solve npm error "npm ERR! code ELIFECYCLE"

Its weird but it works for me

Go to

control panel -->System and Security--> System --> Advanced System Security--> Environment Variables

In Environment Variable popup you will edit the user variable PATH and add "C:\Windows\System32" value as semicolon separated to the existing value.

Not but not least restart the Machine.

enter image description here

SyntaxError: import declarations may only appear at top level of a module

I got this on Firefox (FF58). I fixed this with:

  1. It is still experimental on Firefox (from v54): You have to set to true the variable dom.moduleScripts.enabled in about:config

Source: Import page on mozilla (See Browser compatibility)

  1. Add type="module" to your script tag where you import the js file

<script type="module" src="appthatimports.js"></script>

  1. Import files have to be prefixed (./, /, ../ or http:// before)

import * from "./mylib.js"

For more examples, this blog post is good.

Programmatically navigate using react router V4

My answer is similar to Alex's. I'm not sure why React-Router made this so needlessly complicated. Why should I have to wrap my component with a HoC just to get access to what's essentially a global?

Anyway, if you take a look at how they implemented <BrowserRouter>, it's just a tiny wrapper around history.

We can pull that history bit out so that we can import it from anywhere. The trick, however, is if you're doing server-side rendering and you try to import the history module, it won't work because it uses browser-only APIs. But that's OK because we usually only redirect in response to a click or some other client-side event. Thus it's probably OK to fake it:

// history.js
if(__SERVER__) {
    module.exports = {};
} else {
    module.exports = require('history').createBrowserHistory();

With the help of webpack, we can define some vars so we know what environment we're in:

plugins: [
    new DefinePlugin({
        '__SERVER__': 'false',
        '__BROWSER__': 'true', // you really only need one of these, but I like to have both

And now you can

import history from './history';

From anywhere. It'll just return an empty module on the server.

If you don't want use these magic vars, you'll just have to require in the global object where it's needed (inside your event handler). import won't work because it only works at the top-level.

Can't bind to 'routerLink' since it isn't a known property

You need to add RouterMoudle into imports sections of the module containing the Header component

Convert a JSON Object to Buffer and Buffer to JSON Object back

You need to stringify the json, not calling toString

var buf = Buffer.from(JSON.stringify(obj));

And for converting string to json obj :

var temp = JSON.parse(buf.toString());

LogisticRegression: Unknown label type: 'continuous' using sklearn in python

LogisticRegression is not for regression but classification !

The Y variable must be the classification class,

(for example 0 or 1)

And not a continuous variable,

that would be a regression problem.

ARG or ENV, which one to use in this case?

From Dockerfile reference:

  • The ARG instruction defines a variable that users can pass at build-time to the builder with the docker build command using the --build-arg <varname>=<value> flag.

  • The ENV instruction sets the environment variable <key> to the value <value>.
    The environment variables set using ENV will persist when a container is run from the resulting image.

So if you need build-time customization, ARG is your best choice.
If you need run-time customization (to run the same image with different settings), ENV is well-suited.

If I want to add let's say 20 (a random number) of extensions or any other feature that can be enable|disable

Given the number of combinations involved, using ENV to set those features at runtime is best here.

But you can combine both by:

  • building an image with a specific ARG
  • using that ARG as an ENV

That is, with a Dockerfile including:

ARG var
ENV var=${var}

You can then either build an image with a specific var value at build-time (docker build --build-arg var=xxx), or run a container with a specific runtime value (docker run -e var=yyy)

Consider defining a bean of type 'service' in your configuration [Spring boot]

A class must have the @Component annotation or a derivation of that (like @Service, @Repository etc.) to be recognized as a Spring bean by the component scanning. So if you add @Component to the class, it should solve your problem.

Get element by id - Angular2

A different approach, i.e: You could just do it 'the Angular way' and use ngModel and skip document.getElementById('loginInput').value = '123'; altogether. Instead:

<input type="text" [(ngModel)]="username"/>
<input type="text" [(ngModel)]="password"/>

and in your component you give these values:

username: 'whatever'
password: 'whatever'

this will preset the username and password upon navigating to page.

Refused to display 'url' in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'

This happens because of your application does not allow to append iframe from origin other than your application domain.

If your application have web.config then add the following tag in web.config

            <add name="X-Frame-Options" value="ALLOW" />

This will allow application to append iframe from other origin also. You can also use the following value for X-Frame-Option


Angular2 material dialog has issues - Did you add it to @NgModule.entryComponents?

In my case, I added my component to declarations and entryComponents and got the same errors. I also needed to add MatDialogModule to imports.

How Spring Security Filter Chain works

The Spring security filter chain is a very complex and flexible engine.

Key filters in the chain are (in the order)

  • SecurityContextPersistenceFilter (restores Authentication from JSESSIONID)
  • UsernamePasswordAuthenticationFilter (performs authentication)
  • ExceptionTranslationFilter (catch security exceptions from FilterSecurityInterceptor)
  • FilterSecurityInterceptor (may throw authentication and authorization exceptions)

Looking at the current stable release 4.2.1 documentation, section 13.3 Filter Ordering you could see the whole filter chain's filter organization:

13.3 Filter Ordering

The order that filters are defined in the chain is very important. Irrespective of which filters you are actually using, the order should be as follows:

  1. ChannelProcessingFilter, because it might need to redirect to a different protocol

  2. SecurityContextPersistenceFilter, so a SecurityContext can be set up in the SecurityContextHolder at the beginning of a web request, and any changes to the SecurityContext can be copied to the HttpSession when the web request ends (ready for use with the next web request)

  3. ConcurrentSessionFilter, because it uses the SecurityContextHolder functionality and needs to update the SessionRegistry to reflect ongoing requests from the principal

  4. Authentication processing mechanisms - UsernamePasswordAuthenticationFilter, CasAuthenticationFilter, BasicAuthenticationFilter etc - so that the SecurityContextHolder can be modified to contain a valid Authentication request token

  5. The SecurityContextHolderAwareRequestFilter, if you are using it to install a Spring Security aware HttpServletRequestWrapper into your servlet container

  6. The JaasApiIntegrationFilter, if a JaasAuthenticationToken is in the SecurityContextHolder this will process the FilterChain as the Subject in the JaasAuthenticationToken

  7. RememberMeAuthenticationFilter, so that if no earlier authentication processing mechanism updated the SecurityContextHolder, and the request presents a cookie that enables remember-me services to take place, a suitable remembered Authentication object will be put there

  8. AnonymousAuthenticationFilter, so that if no earlier authentication processing mechanism updated the SecurityContextHolder, an anonymous Authentication object will be put there

  9. ExceptionTranslationFilter, to catch any Spring Security exceptions so that either an HTTP error response can be returned or an appropriate AuthenticationEntryPoint can be launched

  10. FilterSecurityInterceptor, to protect web URIs and raise exceptions when access is denied

Now, I'll try to go on by your questions one by one:

I'm confused how these filters are used. Is it that for the spring provided form-login, UsernamePasswordAuthenticationFilter is only used for /login, and latter filters are not? Does the form-login namespace element auto-configure these filters? Does every request (authenticated or not) reach FilterSecurityInterceptor for non-login url?

Once you are configuring a <security-http> section, for each one you must at least provide one authentication mechanism. This must be one of the filters which match group 4 in the 13.3 Filter Ordering section from the Spring Security documentation I've just referenced.

This is the minimum valid security:http element which can be configured:

<security:http authentication-manager-ref="mainAuthenticationManager" 
    <security:intercept-url pattern="/sectest/zone1/**" access="hasRole('ROLE_ADMIN')"/>

Just doing it, these filters are configured in the filter chain proxy:

        "1": "",
        "2": "",
        "3": "",
        "4": "",
        "5": "",
        "6": "",
        "7": "",
        "8": "",
        "9": "",
        "10": ""

Note: I get them by creating a simple RestController which @Autowires the FilterChainProxy and returns it's contents:

    private FilterChainProxy filterChainProxy;

    public @ResponseBody Map<Integer, Map<Integer, String>> getSecurityFilterChainProxy(){
        return this.getSecurityFilterChainProxy();

    public Map<Integer, Map<Integer, String>> getSecurityFilterChainProxy(){
        Map<Integer, Map<Integer, String>> filterChains= new HashMap<Integer, Map<Integer, String>>();
        int i = 1;
        for(SecurityFilterChain secfc :  this.filterChainProxy.getFilterChains()){
            //filters.put(i++, secfc.getClass().getName());
            Map<Integer, String> filters = new HashMap<Integer, String>();
            int j = 1;
            for(Filter filter : secfc.getFilters()){
                filters.put(j++, filter.getClass().getName());
            filterChains.put(i++, filters);
        return filterChains;

Here we could see that just by declaring the <security:http> element with one minimum configuration, all the default filters are included, but none of them is of a Authentication type (4th group in 13.3 Filter Ordering section). So it actually means that just by declaring the security:http element, the SecurityContextPersistenceFilter, the ExceptionTranslationFilter and the FilterSecurityInterceptor are auto-configured.

In fact, one authentication processing mechanism should be configured, and even security namespace beans processing claims for that, throwing an error during startup, but it can be bypassed adding an entry-point-ref attribute in <http:security>

If I add a basic <form-login> to the configuration, this way:

<security:http authentication-manager-ref="mainAuthenticationManager">
    <security:intercept-url pattern="/sectest/zone1/**" access="hasRole('ROLE_ADMIN')"/>
    <security:form-login />

Now, the filterChain will be like this:

        "1": "",
        "2": "",
        "3": "",
        "4": "",
        "5": "",
        "6": "",
        "7": "",
        "8": "",
        "9": "",
        "10": "",
        "11": "",
        "12": ""

Now, this two filters and are created and configured in the FilterChainProxy.

So, now, the questions:

Is it that for the spring provided form-login, UsernamePasswordAuthenticationFilter is only used for /login, and latter filters are not?

Yes, it is used to try to complete a login processing mechanism in case the request matches the UsernamePasswordAuthenticationFilter url. This url can be configured or even changed it's behaviour to match every request.

You could too have more than one Authentication processing mechanisms configured in the same FilterchainProxy (such as HttpBasic, CAS, etc).

Does the form-login namespace element auto-configure these filters?

No, the form-login element configures the UsernamePasswordAUthenticationFilter, and in case you don't provide a login-page url, it also configures the, which ends in a simple autogenerated login page.

The other filters are auto-configured by default just by creating a <security:http> element with no security:"none" attribute.

Does every request (authenticated or not) reach FilterSecurityInterceptor for non-login url?

Every request should reach it, as it is the element which takes care of whether the request has the rights to reach the requested url. But some of the filters processed before might stop the filter chain processing just not calling FilterChain.doFilter(request, response);. For example, a CSRF filter might stop the filter chain processing if the request has not the csrf parameter.

What if I want to secure my REST API with JWT-token, which is retrieved from login? I must configure two namespace configuration http tags, rights? Other one for /login with UsernamePasswordAuthenticationFilter, and another one for REST url's, with custom JwtAuthenticationFilter.

No, you are not forced to do this way. You could declare both UsernamePasswordAuthenticationFilter and the JwtAuthenticationFilter in the same http element, but it depends on the concrete behaviour of each of this filters. Both approaches are possible, and which one to choose finnally depends on own preferences.

Does configuring two http elements create two springSecurityFitlerChains?

Yes, that's true

Is UsernamePasswordAuthenticationFilter turned off by default, until I declare form-login?

Yes, you could see it in the filters raised in each one of the configs I posted

How do I replace SecurityContextPersistenceFilter with one, which will obtain Authentication from existing JWT-token rather than JSESSIONID?

You could avoid SecurityContextPersistenceFilter, just configuring session strategy in <http:element>. Just configure like this:

<security:http create-session="stateless" >

Or, In this case you could overwrite it with another filter, this way inside the <security:http> element:

<security:http ...>  
   <security:custom-filter ref="myCustomFilter" position="SECURITY_CONTEXT_FILTER"/>    
<beans:bean id="myCustomFilter" class="" />


One question about "You could too have more than one Authentication processing mechanisms configured in the same FilterchainProxy". Will the latter overwrite the authentication performed by first one, if declaring multiple (Spring implementation) authentication filters? How this relates to having multiple authentication providers?

This finally depends on the implementation of each filter itself, but it's true the fact that the latter authentication filters at least are able to overwrite any prior authentication eventually made by preceding filters.

But this won't necesarily happen. I have some production cases in secured REST services where I use a kind of authorization token which can be provided both as a Http header or inside the request body. So I configure two filters which recover that token, in one case from the Http Header and the other from the request body of the own rest request. It's true the fact that if one http request provides that authentication token both as Http header and inside the request body, both filters will try to execute the authentication mechanism delegating it to the manager, but it could be easily avoided simply checking if the request is already authenticated just at the begining of the doFilter() method of each filter.

Having more than one authentication filter is related to having more than one authentication providers, but don't force it. In the case I exposed before, I have two authentication filter but I only have one authentication provider, as both of the filters create the same type of Authentication object so in both cases the authentication manager delegates it to the same provider.

And opposite to this, I too have a scenario where I publish just one UsernamePasswordAuthenticationFilter but the user credentials both can be contained in DB or LDAP, so I have two UsernamePasswordAuthenticationToken supporting providers, and the AuthenticationManager delegates any authentication attempt from the filter to the providers secuentially to validate the credentials.

So, I think it's clear that neither the amount of authentication filters determine the amount of authentication providers nor the amount of provider determine the amount of filters.

Also, documentation states SecurityContextPersistenceFilter is responsible of cleaning the SecurityContext, which is important due thread pooling. If I omit it or provide custom implementation, I have to implement the cleaning manually, right? Are there more similar gotcha's when customizing the chain?

I did not look carefully into this filter before, but after your last question I've been checking it's implementation, and as usually in Spring, nearly everything could be configured, extended or overwrited.

The SecurityContextPersistenceFilter delegates in a SecurityContextRepository implementation the search for the SecurityContext. By default, a HttpSessionSecurityContextRepository is used, but this could be changed using one of the constructors of the filter. So it may be better to write an SecurityContextRepository which fits your needs and just configure it in the SecurityContextPersistenceFilter, trusting in it's proved behaviour rather than start making all from scratch.

Could not find a declaration file for module 'module-name'. '/path/to/module-name.js' implicitly has an 'any' type

I was getting this too, had me baffled for a while, even with the module and types already installed and reloading my IDE several times.

What fixed it in my case was terminating terminal processes, removing node_modules, clearing the node package manager cache and doing a fresh install then re-loading the editor.

Angular2 module has no exported member

For my case, I restarted the server and it worked.

angular2: Error: TypeError: Cannot read property '...' of undefined

Safe navigation operator or Existential Operator or Null Propagation Operator is supported in Angular Template. Suppose you have Component class

  myObj:any = {
    doSomething: function () { console.log('doing something'); return 'doing something'; },
  constructor() { }

  ngOnInit() {
    this.myArray = [this.myObj];

You can use it in template html file as following:

<div>test-1: {{  myObj?.doSomething()}}</div>
<div>test-2: {{  myArray[0].doSomething()}}</div>
<div>test-3: {{  myArray[2]?.doSomething()}}</div>

can not find module "@angular/material"

Please check Angular Getting started :)

  1. Install Angular Material and Angular CDK
  2. Animations - if you need
  3. Import the component modules

and enjoy the {{Angular}}

How to declare a Fixed length Array in TypeScript

The javascript array has a constructor that accepts the length of the array:

let arr = new Array<number>(3);
console.log(arr); // [undefined × 3]

However, this is just the initial size, there's no restriction on changing that:

console.log(arr); // [undefined × 3, 5]

Typescript has tuple types which let you define an array with a specific length and types:

let arr: [number, number, number];

arr = [1, 2, 3]; // ok
arr = [1, 2]; // Type '[number, number]' is not assignable to type '[number, number, number]'
arr = [1, 2, "3"]; // Type '[number, number, string]' is not assignable to type '[number, number, number]'

How to define Typescript Map of key value pair. where key is a number and value is an array of objects

The most simple way is to use Record type Record<number, productDetails >

interface productDetails {
   productId : number , 
   price : number , 
   discount : number

const myVar : Record<number, productDetails> = {
   1: {
       productId : number , 
       price : number , 
       discount : number

Changing background color of selected item in recyclerview

I was able to change the selected view color like this. I think this is the SIMPLE WAY (because you don't have to create instance of layouts and variables.



onBindViewHolder() method is given below

public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {

        holder.select_cb.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

                if (isChecked){

                }else {


How to use onClick with divs in React.js

This also works:

I just changed with this.state.color==='white'?'black':'white'.

You can also pick the color from drop-down values and update in place of 'black';


How to create a fixed sidebar layout with Bootstrap 4?

I'm using the J.S. to fix a sidebar menu. I've tried a lot of solutions with CSS but it's the simplest way to solve it, just add J.S. adding and removing a native BootStrap class: "position-fixed".

The J.S.:

var lateral = false;
function fixar() {

            var element, name, arr;
            element = document.getElementById("minhasidebar");

            if (lateral) {
                element.className = element.className.replace(
                        /\bposition-fixed\b/g, "");
                lateral = false;
            } else {

                name = "position-fixed";
                arr = element.className.split(" ");
                if (arr.indexOf(name) == -1) {
                    element.className += " " + name;
                lateral = true;




        <nav class="sidebar ">
             <div id="minhasidebar">
                 <ul class="nav nav-pills">
                     <li class="nav-item"><a class="nav-link active" 
                     th:href="@{/hoje/inicial}"> <i class="oi oi-clipboard"></i> 

Angular2: custom pipe could not be found

see this is working for me.

ActStatus.pipe.ts First this is my pipe

import {Pipe,PipeTransform} from "@angular/core";

export class ActStatusPipe implements PipeTransform{
    switch (status) {
      case 1:
        return "UN_PUBLISH";
      case 2:
        return "PUBLISH";
        return status

main-pipe.module.ts in pipe module, i need to declare my pipe/s and export it.

import { NgModule } from '@angular/core';
import {CommonModule} from "@angular/common";

import {ActStatusPipe} from "./ActStatusPipe.pipe"; // <---

  declarations:[ActStatusPipe], // <---
  exports:[ActStatusPipe] // <---

export class MainPipe{}

app.module.ts user this pipe module in any module.

  declarations: [...],
  imports: [..., MainPipe], // <---
  providers: [...],
  bootstrap: [AppComponent]

you can directly user pipe in this module. but if you feel that your pipe is used with in more than one component i suggest you to follow my approach.

  1. create pipe .
  2. create separate module and declare and export one or more pipe.
  3. user that pipe module.

How to use pipe totally depends on your project complexity and requirement. you might have just one pipe which used only once in the whole project. in that case you can directly use it without creating a pipe/s module (module approach).

How to suppress "error TS2533: Object is possibly 'null' or 'undefined'"?

This solution worked for me:

  • go to tsconfig.json and add "strictNullChecks":false

enter image description here

Deserialize Java 8 LocalDateTime with JacksonMapper


Change to:

@Column(name = "start_date")
@DateTimeFormat(pattern = "yyyy-MM-dd HH:mm", iso = ISO.DATE_TIME)
@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm")
private LocalDateTime startDate;

JSON request:

 "startDate":"2019-04-02 11:45"

Django model "doesn't declare an explicit app_label"

I got this error while trying to upgrade my Django Rest Framework app to DRF 3.6.3 and Django 1.11.1.

For anyone else in this situation, I found my solution in a GitHub issue, which was to unset the UNAUTHENTICATED_USER setting in the DRF settings:

# webapp/

Error creating bean with name 'entityManagerFactory' defined in class path resource : Invocation of init method failed

For those who use Gradle instead of Maven, add this to the dependencies in your build file:


How to Upload Image file in Retrofit 2

Using Retrofit 2.0 you may use this:

    Call<ResponseBody> uploadImage(@Part("file\"; fileName=\"myFile.png\" ")RequestBody requestBodyFile, @Part("image") RequestBody requestBodyJson);

Make a request:

File imgFile = new File("YOUR IMAGE FILE PATH");
RequestBody requestBodyFile = RequestBody.create(MediaType.parse("image/*"), imgFile);
RequestBody requestBodyJson = RequestBody.create(MediaType.parse("text/plain"),

//make sync call
Call<ResponseBody> uploadBundle = uploadImpl.uploadImage(requestBodyFile, requestBodyJson);
Response<BaseResponse> response = uploadBundle.execute();

please refer

Jenkins: Cannot define variable in pipeline stage

Agree with @Pom12, @abayer. To complete the answer you need to add script block

Try something like this:

pipeline {
    agent any
    environment {
        ENV_NAME = "${env.BRANCH_NAME}"

    // ----------------

    stages {
        stage('Build Container') {
            steps {
                echo 'Building Container..'

                script {
                    if (ENVIRONMENT_NAME == 'development') {
                        ENV_NAME = 'Development'
                    } else if (ENVIRONMENT_NAME == 'release') {
                        ENV_NAME = 'Production'
                echo 'Building Branch: ' + env.BRANCH_NAME
                echo 'Build Number: ' + env.BUILD_NUMBER
                echo 'Building Environment: ' + ENV_NAME

                echo "Running your service with environemnt ${ENV_NAME} now"

Import JSON file in React

The solution that worked for me is that:- I moved my data.json file from src to public directory. Then used fetch API to fetch the file

fetch('./data.json').then(response => {
      return response.json();
    }).then(data => {
      // Work with JSON data here
    }).catch(err => {
      // Do something for an error here
      console.log("Error Reading data " + err);

The problem was that after compiling react app the fetch request looks for the file at URL "http://localhost:3000/data.json" which is actually the public directory of my react app. But unfortunately while compiling react app data.json file is not moved from src to public directory. So we have to explicitly move data.json file from src to public directory.

Angular 2 : No NgModule metadata found

I had the same problem but none of all those solutions worked for me. After further investigation, I found out that an undesired import was in one of my component.

I use setTimeout function in app.component but for any reason Visual Studio added import { setTimeout } from 'timer'; where it was not needed. Removing this line fixed the issue.

So remember to check your imports before going further. Hope it may help someone.

Class constructor type in typescript?

Like that:

class Zoo {
    AnimalClass: typeof Animal;

    constructor(AnimalClass: typeof Animal ) {
        this.AnimalClass = AnimalClass
        let Hector = new AnimalClass();

Or just:

class Zoo {
    constructor(public AnimalClass: typeof Animal ) {
        let Hector = new AnimalClass();

typeof Class is the type of the class constructor. It's preferable to the custom constructor type declaration because it processes static class members properly.

Here's the relevant part of TypeScript docs. Search for the typeof. As a part of a TypeScript type annotation, it means "give me the type of the symbol called Animal" which is the type of the class constructor function in our case.

Use component from another module

Note that in order to create a so called "feature module", you need to import CommonModule inside it. So, your module initialization code will look like this:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

import { TaskCardComponent } from './task-card/task-card.component';
import { MdCardModule } from '@angular2-material/card';

  imports: [
  declarations: [
  exports: [
export class TaskModule { }

More information available here:

Debug/run standard java in Visual Studio Code IDE and OS X?

There is a much easier way to run Java, no configuration needed:

  1. Install the Code Runner Extension
  2. Open your Java code file in Text Editor, then use shortcut Ctrl+Alt+N, or press F1 and then select/type Run Code, or right click the Text Editor and then click Run Code in context menu, the code will be compiled and run, and the output will be shown in the Output Window.


How to create unique keys for React elements?

I am using this:

<div key={+new Date() + Math.random()}>

CUSTOM_ELEMENTS_SCHEMA added to NgModule.schemas still showing Error

With components containing Angular Material, a similar error came up with my unit tests. As per @Dan Stirling-Talbert's answer above, added this to my component .spec file and the error was cleared from my unit tests.

Import { CUSTOM_ELEMENTS_SCHEMA } from '@angular/core'

Then add the schema in the generated beforeEach() statement:

beforeEach(asyn(() => {
    declarations: [ AboutComponent ],

My Karma error was: If 'mat-panel-title' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.

How to import component into another root component in Angular 2

Angular RC5 & RC6

If you are getting the above mentioned error in your Jasmine tests, it is most likely because you have to declare the unrenderable component in your TestBed.configureTestingModule({}).

The TestBed configures and initializes an environment for unit testing and provides methods for mocking/creating/injecting components and services in unit tests.

If you don't declare the component before your unit tests are executed, Angular will not know what <courses></courses> is in your template file.

Here is an example:

import {async, ComponentFixture, TestBed} from "@angular/core/testing";
import {AppComponent} from "../app.component";
import {CoursesComponent} from './courses.component';

describe('CoursesComponent', () => {
  let component: CoursesComponent;
  let fixture: ComponentFixture<CoursesComponent>;

  beforeEach(async(() => {
      declarations: [
      imports: [
        // If you have any other imports add them here

  beforeEach(() => {
    fixture = TestBed.createComponent(CoursesComponent);
    component = fixture.componentInstance;

  it('should create', () => {

Angular 2 declaring an array of objects

type NumberArray = Array<{id: number, text: string}>;

const arr: NumberArray = [
    {id: 0, text: 'Number 0'},
    {id: 1, text: 'Number 1'},
    {id: 2, text: 'Number 2'},
    {id: 3, text: 'Number 3 '},
    {id: 4, text: 'Number 4 '},
    {id: 5, text: 'Number 5 '},

Angular2 RC6: '<component> is not a known element'

I received this error when I imported Module A into Module B, and then tried to use a component from Module A in Module B.

The solution is to declare that component in the exports array.

  declarations: [
  exports: [
export class ModuleA {}
  imports: [
export class ModuleB {}

Error: Unexpected value 'undefined' imported by the module

I had this error because I had an index.ts file in the root of my app that was exporting my app.component.ts. So I thought I could do the following:

import { AppComponent } from './';

This worked and gave me no red squiggly lines and even intellisense brings up AppComponent when you start typing it. But come to find out it was causing this error. After I changed it to:

import { AppComponent } from './app.component';

The error went away.

Can't bind to 'formGroup' since it isn't a known property of 'form'

You need to import the FormsModule, ReactiveFormsModule in this module as well as the top level.

If you used a reactiveForm in another module then you've to do also this step along with above step: import also reactiveFormsModule in that particular module.

For example:

imports: [

What is the difference between declarations, providers, and import in NgModule?

Adding a quick cheat sheet that may help after the long break with Angular:



declarations: [AppComponent]

What can we inject here? Components, pipes, directives



imports: [BrowserModule, AppRoutingModule]

What can we inject here? other modules



providers: [UserService]

What can we inject here? services



bootstrap: [AppComponent]

What can we inject here? the main component that will be generated by this module (top parent node for a component tree)



entryComponents: [PopupComponent]

What can we inject here? dynamically generated components (for instance by using ViewContainerRef.createComponent())



export: [TextDirective, PopupComponent, BrowserModule]

What can we inject here? components, directives, modules or pipes that we would like to have access to them in another module (after importing this module)

Swift 3 - Comparing Date objects

To compare date only with year - month - day and without time for me worked like this:

     let order =, to: compareDate!, toGranularity: .day)  

                      switch order {
                        case .orderedAscending:
                            print("\(gpsDate) is after \(self.startDate)")
                        case .orderedDescending:
                            print("\(gpsDate) is before \(self.startDate)")
                            print("\(gpsDate) is the same as \(self.startDate)")

No value accessor for form control with name: 'recipient'

Make sure you import MaterialModule as well since you are using md-input which does not belong to FormsModule

Angular2 RC5: Can't bind to 'Property X' since it isn't a known property of 'Child Component'

I ran into the same error, when I just forgot to declare my custom component in my NgModule - check there, if the others solutions won't work for you.

Unknown lifecycle phase "mvn". You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id>

Thanks for the reply. I was using "mvn clean install" in the maven build configuration. we no need to use "mvn" command if running through eclipse.

After buiding the application using the command "clean install" , I got one more error -
"No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?"

I followed this link:- No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?

now application building is fine in eclipse.

Specifying java version in maven - differences between properties and compiler plugin

Consider the alternative:


It should be the same thing of maven.compiler.source/ but the above solution works for me, otherwise the second one gets the parent specification (I have a matrioska of .pom)

Declare an array in TypeScript

this is how you can create an array of boolean in TS and initialize it with false:

var array: boolean[] = [false, false, false]

or another approach can be:

var array2: Array<boolean> =[false, false, false] 

you can specify the type after the colon which in this case is boolean array

React Native: Possible unhandled promise rejection

You should add the catch() to the end of the Api call. When your code hits the catch() it doesn't return anything, so data is undefined when you try to use setState() on it. The error message actually tells you this too :)

Can't push to the heroku

Specify the buildpack while creating the app.

heroku create appname --buildpack heroku/python

implement addClass and removeClass functionality in angular2

Try to use it via [ngClass] property:

<div class="button" [ngClass]="{active: isOn, disabled: isDisabled}"
         Click me!

React - how to pass state to another component

Move all of your state and your handleClick function from Header to your MainWrapper component.

Then pass values as props to all components that need to share this functionality.

class MainWrapper extends React.Component {
    constructor() {
        this.state = {
            sidbarPushCollapsed: false,
            profileCollapsed: false
        this.handleClick = this.handleClick.bind(this);
    handleClick() {
            sidbarPushCollapsed: !this.state.sidbarPushCollapsed,
            profileCollapsed: !this.state.profileCollapsed

    render() {
        return (
               profileCollapsed={this.state.profileCollapsed} />

Then in your Header's render() method, you'd use this.props:

<button type="button" id="sidbarPush" onClick={this.props.handleClick} profile={this.props.profileCollapsed}>

React eslint error missing in props validation

I ran into this issue over the past couple days. Like Omri Aharon said in their answer above, it is important to add definitions for your prop types similar to:

SomeClass.propTypes = {
    someProp: PropTypes.number,
    onTap: PropTypes.func,

Don't forget to add the prop definitions outside of your class. I would place it right below/above my class. If you are not sure what your variable type or suffix is for your PropType (ex: PropTypes.number), refer to this npm reference. To Use PropTypes, you must import the package:

import PropTypes from 'prop-types';

If you get the linting error:someProp is not required, but has no corresponding defaultProps declaration all you have to do is either add .isRequired to the end of your prop definition like so:

SomeClass.propTypes = {
    someProp: PropTypes.number.isRequired,
    onTap: PropTypes.func.isRequired,

OR add default prop values like so:

SomeClass.defaultProps = {
    someProp: 1

If you are anything like me, unexperienced or unfamiliar with reactjs, you may also get this error: Must use destructuring props assignment. To fix this error, define your props before they are used. For example:

const { someProp } = this.props;

React prevent event bubbling in nested components on click

This is not 100% ideal, but if it is either too much of a pain to pass down props in children -> children fashion or create a Context.Provider/Context.Consumer just for this purpose), and you are dealing with another library which has it's own handler it runs before yours, you can also try:

   function myHandler(e) { 

From what I understand, the event.persist method prevents an object from immediately being thrown back into React's SyntheticEvent pool. So because of that, the event passed in React actually doesn't exist by the time you reach for it! This happens in grandchildren because of the way React handle's things internally by first checking parent on down for SyntheticEvent handlers (especially if the parent had a callback).

As long as you are not calling persist on something which would create significant memory to keep creating events such as onMouseMove (and you are not creating some kind of Cookie Clicker game like Grandma's Cookies), it should be perfectly fine!

Also note: from reading around their GitHub occasionally, we should keep our eyes out for future versions of React as they may eventually resolve some of the pain with this as they seem to be going towards making folding React code in a compiler/transpiler.

How to declare a variable in a template in Angular

If you need autocomplete support from within in your templates from the Angular Language Service:


myVar = { hello: '' };

<ng-container *ngIf="myVar; let var;">

Using async pipe:

myVar$ = of({ hello: '' });

<ng-container *ngIf="myVar$ | async; let var;">

How to get input text value on click in ReactJS

First of all, you can't pass to alert second argument, use concatenation instead

alert("Input is " + inputValue);


However in order to get values from input better to use states like this

var MyComponent = React.createClass({_x000D_
  getInitialState: function () {_x000D_
    return { input: '' };_x000D_
  handleChange: function(e) {_x000D_
    this.setState({ input: });_x000D_
  handleClick: function() {_x000D_
  render: function() {_x000D_
    return (_x000D_
        <input type="text" onChange={ this.handleChange } />_x000D_
          value="Alert the text input"_x000D_
  <MyComponent />,_x000D_
<script src=""></script>_x000D_
<script src=""></script>_x000D_
<div id="container"></div>

How do I declare a model class in my Angular 2 component using TypeScript?

The problem lies that you haven't added Model to either the bootstrap (which will make it a singleton), or to the providers array of your component definition:

    selector: "testWidget",
    template: "<div>This is a test and {{param1}} is my param.</div>",
    providers : [

export class testWidget {
    constructor(private model: Model) {}

And yes, you should define Model above the Component. But better would be to put it in his own file.

But if you want it to be just a class from which you can create multiple instances, you better just use new.

    selector: "testWidget",
    template: "<div>This is a test and {{param1}} is my param.</div>"

export class testWidget {

    private model: Model = new Model();

    constructor() {}

How to pass data from child component to its parent in ReactJS?

Considering React Function Components and using Hooks are getting more popular these days , I will give a simple example of how to Passing data from child to parent component

in Parent Function Component we will have :

import React, { useState, useEffect } from "react";


const [childData, setChildData] = useState("");

and passing setChildData (which do a job similar to this.setState in Class Components) to Child

return( <ChildComponent passChildData={setChildData} /> )

in Child Component first we get the receiving props

function ChildComponent(props){ return (...) }

then you can pass data anyhow like using a handler function

const functionHandler = (data) => {



Check if element is clickable in Selenium Java

wait.until(ExpectedConditions) won't return null, it will either meet the condition or throw TimeoutException.

You can check if the element is displayed and enabled

WebElement element = driver.findElement(By.xpath);
if (element.isDisplayed() && element.isEnabled()) {;

Rendering an in React

import React, { Component } from 'react';

class Result extends Component {

    render() {


            var foodlist =>{

                   return (

                   <div className="row" key={} >

                  <div className="list-group">   

                  <a href="#" className="list-group-item list-group-item-action disabled">

                  <span className="badge badge-info"><h6> {name.item}</h6></span>
                  <span className="badge badge-danger"><h6> Rs.{name.price}/=</h6></span>

                  <a href="#" className="list-group-item list-group-item-action disabled">
                  <div className="alert alert-dismissible alert-secondary">

                <div className="form-group">

                    <label className="col-form-label col-form-label-sm" htmlFor="inputSmall">Quantitiy</label>
                    <input className="form-control form-control-sm" placeholder="unit/kg"  type="text" ref="qty"/>
                    <div> <button type="button" className="btn btn-success"  
                    }>ADD Cart</button>







        return (

export default Result;

Visual Studio Code Automatic Imports

Typescript Importer does do the job for me

It automatically searches for typescript definitions inside your workspace and when you press enter it'll import it.

How to access a DOM element in React? What is the equilvalent of document.getElementById() in React

You can do that by specifying the ref

EDIT: In react v16.8.0 with function component, you can define a ref with useRef. Note that when you specify a ref on a function component, you need to use React.forwardRef on it to forward the ref to the DOM element of use useImperativeHandle to to expose certain functions from within the function component


const Child1 = React.forwardRef((props, ref) => {
    return <div ref={ref}>Child1</div> 

const Child2 = React.forwardRef((props, ref) => {
    const handleClick= () =>{};
    useImperativeHandle(ref,() => ({
    return <div>Child2</div> 
const App = () => {
    const child1 = useRef(null);
    const child2 = useRef(null);

    return (
           <Child1 ref={child1} />
           <Child1 ref={child1} />


In React 16.3+, use React.createRef() to create your ref:

class MyComponent extends React.Component {
  constructor(props) {
    this.myRef = React.createRef();
  render() {
    return <div ref={this.myRef} />;

In order to access the element, use:

const node = this.myRef.current;

DOC for using React.createRef()


However facebook advises against it because string refs have some issues, are considered legacy, and are likely to be removed in one of the future releases.

From the docs:

Legacy API: String Refs

If you worked with React before, you might be familiar with an older API where the ref attribute is a string, like "textInput", and the DOM node is accessed as this.refs.textInput. We advise against it because string refs have some issues, are considered legacy, and are likely to be removed in one of the future releases. If you're currently using this.refs.textInput to access refs, we recommend the callback pattern instead.

A recommended way for React 16.2 and earlier is to use the callback pattern:

<Progressbar completed={25} id="Progress1" ref={(input) => {this.Progress[0] = input }}/>

<h2 class="center"></h2>

<Progressbar completed={50} id="Progress2" ref={(input) => {this.Progress[1] = input }}/>

  <h2 class="center"></h2>

<Progressbar completed={75} id="Progress3" ref={(input) => {this.Progress[2] = input }}/>

DOC for using callback

Even older versions of react defined refs using string like below

<Progressbar completed={25} id="Progress1" ref="Progress1"/>

    <h2 class="center"></h2>

    <Progressbar completed={50} id="Progress2" ref="Progress2"/>

      <h2 class="center"></h2>

    <Progressbar completed={75} id="Progress3" ref="Progress3"/>

In order to get the element just do

var object = this.refs.Progress1;

Remember to use this inside an arrow function block like:

print = () => {
  var object = this.refs.Progress1;  

and so on...

How to install and run Typescript locally in npm?

You can now use ts-node, which makes your life as simple as

npm install -D ts-node
npm install -D typescript

ts-node script.ts

How to check whether Kafka Server is running?

For Linux, "ps aux | grep kafka" see if kafka properties are shown in the results. E.g. /path/to/kafka/

Why was the name 'let' chosen for block-scoped variable declarations in JavaScript?

I think JavaScript's indebtedness to Scheme is obvious here. Scheme not only has let, but has let*, let*-values, let-syntax, and let-values. (See, The Scheme Programming Language, 4th Ed.).

((The choice adds further credence to the notion that JavaScript is Lispy, but--before we get carried away--not homoiconic.))))

How to create empty constructor for data class in Kotlin Android

the modern answer for this should be using Kotlin's no-arg compiler plugin which creates a non argument construct code for classic apies more about here

simply you have to add the plugin class path in build.gradle project level

    dependencies {

    classpath "org.jetbrains.kotlin:kotlin-noarg:1.4.10"


then configure your annotation to generate the no-arg constructor

apply plugin: "kotlin-noarg"

noArg {
      invokeInitializers = true

then define your annotation file NoArg.kt

 annotation class NoArg

finally in any data class you can simply use your own annotation

data class SomeClass( val datafield:Type , ...   )

I used to create my own no-arg constructor as the accepted answer , which i got by search but then this plugin released or something and I found it way cleaner .

console.log not working in Angular2 Component (Typescript)

The console.log should be wrapped in a function , the "default" function for every class is its constructor so it should be declared there.

import { Component } from '@angular/core';

  selector: 'hello-console',
    export class App {
     s: string = "Hello2";


Using an array from Observable Object with ngFor and Async Pipe Angular 2

Who ever also stumbles over this post.

I belive is the correct way:

  <div *ngFor="let appointment of (_nextFourAppointments | async).availabilities;"> 
    <div>{{ appointment }}</div>

Adb install failure: INSTALL_CANCELED_BY_USER

Its a Xiaomi's issue If possible update MIUI to latest version then go to Settings > Additional Settings > Developer Options > Developer options: Check the Install via USB option.

This solved my issue hope it will also solve yours good luck!

What does 'Unsupported major.minor version 52.0' mean, and how do I fix it?

You don't need to change the compliance level here, or rather, you should but that's not the issue.

The code compliance ensures your code is compatible with a given Java version.

For instance, if you have a code compliance targeting Java 6, you can't use Java 7's or 8's new syntax features (e.g. the diamond, the lambdas, etc. etc.).

The actual issue here is that you are trying to compile something in a Java version that seems different from the project dependencies in the classpath.

Instead, you should check the JDK/JRE you're using to build.

In Eclipse, open the project properties and check the selected JRE in the Java build path.

If you're using custom Ant (etc.) scripts, you also want to take a look there, in case the above is not sufficient per se.

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformClassesWithDexForDebug'

For my case, I follow the steps from Firebase and by mistake I pated it in a wrong file.

Then, I returned to the project from Project to Android. Once in the Android view I pasted the file /projectname/app/YOUR-FILE-HERE and now, you have to compile again.

ReactNative: how to center text?

In addition to the use cases mentioned in the other answers:

To center text in the specific use case of a BottomTabNavigator, remember to set showIcon to false (even if you don't have icons in the TabNavigator). Otherwise the text will be pushed toward bottom of Tab.

For example:

const TabNavigator = createBottomTabNavigator({
  Home: HomeScreen,
  Settings: SettingsScreen
}, {
  tabBarOptions: {
    activeTintColor: 'white',
    inactiveTintColor: 'black',
    showIcon: false, //do this
    labelStyle: {
      fontSize: 20,
      textAlign: 'center',
    tabStyle: {
      backgroundColor: 'grey',
      marginTop: 0,
      textAlign: 'center',
      justifyContent: 'center',
      textAlignVertical: "center"

m2e error in MavenArchiver.getManifest()

I found my answer! I looked into the pom for any plugins that have a dependency on the maven-archiver and found the maven-jar-plugin does. It was using the latest 3.0.0 version. When I downgraded to 2.6 it seems to fix the issue :-)

How do I download the Android SDK without downloading Android Studio?

This tutorial is a just step by step for installing Android SDK (Software Development Kit) assuming the user is starting from scratch.

There are just a couple of prerequisites to note:

  • Java runtime environment (or JDK) at Oracle website (and download the correct version (32- or 64-bit) for your computer).
  • A good internet connection (needed for downloading system images etc)

I recommed using the offline SDK installer for installing the essential tools namely SDK and AVD manager: The last version of he installer is found here: SDK Installer_r24.4.1 (for windows), SDK Installer_r24.4.1 (for linux) or SDK Installer_r24.4.1 (for macos)

For this guide I was using windows:

Here is the workthrough:

  • Depending on your choice download the appropriate SDK package from above links (but for this example I will be using the manual method)
  • After downloading the package, begin installation (and choose the desired installation folder to proceed or just leave the default %USERPROFILE%\android-sdk):

enter image description here

  • When done leave the option to download system images "checked":

enter image description here

Now we're in business...

  • The SDK manager window will appear, now you need to update/download other sdk packages (i.e platform-tools, system-images, platforms etc according to API levels)

enter image description here

Note: I recommend downloading x86 images as they're much faster tham arm counterparts, also get intel HAXM (hardware accelerated execution manager) driver to significantly increase your emulator speed

  • All set, now you just need to create and configure an Android virtual device matching your target Android version and tweak desired settings.

  • To do this click on the Tools tab in SDK manager and select manage AVDs, then in the following window click Create you'll see a similar screen as below:

enter image description here

  • After that boot the newly created virtual device.

enter image description here

  • Install applications and test as you wish ..

Error:Execution failed for task ':app:transformClassesWithDexForDebug' in android studio

For Ionic 4 Just

$ cordova clean

Helped me then run

$ ionic cordova run android --device

What is the best way to declare global variable in Vue.js?

In vue cli-3 You can define the variable in main.js like


And you can also access this variable in any component by using the the window.basurl

React.js: Set innerHTML vs dangerouslySetInnerHTML

Yes there is a difference!

The immediate effect of using innerHTML versus dangerouslySetInnerHTML is identical -- the DOM node will update with the injected HTML.

However, behind the scenes when you use dangerouslySetInnerHTML it lets React know that the HTML inside of that component is not something it cares about.

Because React uses a virtual DOM, when it goes to compare the diff against the actual DOM, it can straight up bypass checking the children of that node because it knows the HTML is coming from another source. So there's performance gains.

More importantly, if you simply use innerHTML, React has no way to know the DOM node has been modified. The next time the render function is called, React will overwrite the content that was manually injected with what it thinks the correct state of that DOM node should be.

Your solution to use componentDidUpdate to always ensure the content is in sync I believe would work but there might be a flash during each render.

Notification Icon with the new Firebase Cloud Messaging system

write this

         android:resource="@drawable/ic_notification" />

right down <application.....>

enter image description here

IntelliJ cannot find any declarations

IDEA may ignore some of your maven dependency files. The "External Libraries" node in your project structure might be empty or incomplete.

Go to:

  1. IntelliJ --> Preferences
  2. Search for Maven [on the left tab] -> Ignored Files
  3. See if there is any path on the right side that is checked(ignored) and uncheck that.enter image description here

"SyntaxError: Unexpected token < in JSON at position 0"

For some, this may help you guys: I had a similar experience with Wordpress REST API. I even used Postman to check if I had the correct routes or endpoint. I later found out that I accidentally put an "echo" inside my script - hooks:

Debug & check your console

Cause of the error

So basically, this means that I printed a value that isn't JSON that is mixed with the script that causes AJAX error - "SyntaxError: Unexpected token r in JSON at position 0"

How to implement class constants?

Angular 2 Provides a very nice feature called as Opaque Constants. Create a class & Define all the constants there using opaque constants.

import { OpaqueToken } from "@angular/core";

export let APP_CONFIG = new OpaqueToken("my.config");

export interface MyAppConfig {
    apiEndpoint: string;

export const AppConfig: MyAppConfig = {    
    apiEndpoint: "http://localhost:8080/api/"    

Inject it in providers in app.module.ts

You will be able to use it across every components.

EDIT for Angular 4 :

For Angular 4 the new concept is Injection Token & Opaque token is Deprecated in Angular 4.

Injection Token Adds functionalities on top of Opaque Tokens, it allows to attach type info on the token via TypeScript generics, plus Injection tokens, removes the need of adding @Inject

Example Code

Angular 2 Using Opaque Tokens

const API_URL = new OpaqueToken('apiUrl'); //no Type Check

providers: [
    provide: DataService,
    useFactory: (http, apiUrl) => {
      // create data service
    deps: [
      new Inject(API_URL) //notice the new Inject

Angular 4 Using Injection Tokens

const API_URL = new InjectionToken<string>('apiUrl'); // generic defines return value of injector

providers: [
    provide: DataService,
    useFactory: (http, apiUrl) => {
      // create data service
    deps: [
      API_URL // no `new Inject()` needed!

Injection tokens are designed logically on top of Opaque tokens & Opaque tokens are deprecated in Angular 4.

Vue.JS: How to call function after page loaded?

Vue watch() life-cycle hook, can be used


<div id="demo">{{ fullName }}</div>


var vm = new Vue({
  el: '#demo',
  data: {
    firstName: 'Foo',
    lastName: 'Bar',
    fullName: 'Foo Bar'
  watch: {
    firstName: function (val) {
      this.fullName = val + ' ' + this.lastName
    lastName: function (val) {
      this.fullName = this.firstName + ' ' + val

How to use Tomcat 8.5.x and TomEE 7.x with Eclipse?

There is a patch for Eclipse:

Download this patch and put it to the plugins directory of your Eclipse installation. It will replace the default "org.eclipse.jst.server.tomcat.core_1.1.800.v201602282129.jar".

After you add this patch you must choose "Apache Tomcat v9.0" when adding a server runtime environment in the Eclipse (Preferences > Server > Runtime Environments).
I.e. this patch allows you to select either Tomcat version 9.x or Tomcat version 8.5.x when adding Apache Tomcat v.9.0 runtime environment.

More details on can be found on the related bug report page:

The type cannot be resolved. It is indirectly referenced from required .class files

Something happened in Java 8 Update 91 that broke existing JSP code. That seems pretty clear. Here is a sample of similar questions and bug reports:

All these are about problems with Java 8 Update 91 (or later) that are not present when using earlier JRE/JDK versions.

The following OpenJDK changeset from 22 January 2016 appears to be related: (commit message "8144430: Improve JMX connections"). The changeset seems to be related to this vulnerability,, which is mentioned in a comment to this Red Hat bug report,

The Update 91 release notes document mentions JDK-8144430 (non-public ticket):

In "Oracle Critical Patch Update Advisory - April 2016", the CVE-2016-3427 vulnerability is mentioned:

Angular 2 beta.17: Property 'map' does not exist on type 'Observable<Response>'

Rxjs 5.5 “ Property ‘map’ does not exist on type Observable.

The problem was related to the fact that you need to add pipe around all operators.

Change this,

this.myObservable().map(data => {})

to this

this.myObservable().pipe(map(data => {}))


Import map like this,

import { map } from 'rxjs/operators';

It will solve your issues.

What are functional interfaces used for in Java 8?

Beside other answers, I think the main reason to "why using Functional Interface other than directly with lambda expressions" can be related to nature of Java language which is Object Oriented.

The main attributes of Lambda expressions are: 1. They can be passed around 2. and they can executed in future in specific time (several times). Now to support this feature in languages, some other languages deal simply with this matter.

For instance in Java Script, a function (Anonymous function, or Function literals) can be addressed as a object. So, you can create them simply and also they can be assigned to a variable and so forth. For example:

var myFunction = function (...) {

or via ES6, you can use an arrow function.

const myFunction = ... => ...

Up to now, Java language designers have not accepted to handle mentioned features via these manner (functional programming techniques). They believe that Java language is Object Oriented and therefore they should solve this problem via Object Oriented techniques. They don't want to miss simplicity and consistency of Java language.

Therefore, they use interfaces, as when an object of an interface with just one method (I mean functional interface) is need you can replace it with a lambda expression. Such as:

ActionListener listener = event -> ...;

installing python packages without internet and using source code as .tar.gz and .whl

If you want to install a bunch of dependencies from, say a requirements.txt, you would do:

mkdir dependencies
pip download -r requirements.txt -d "./dependencies"
tar cvfz dependencies.tar.gz dependencies

And, once you transfer the dependencies.tar.gz to the machine which does not have internet you would do:

tar zxvf dependencies.tar.gz
cd dependencies
pip install * -f ./ --no-index

Dynamically add child components in React

Sharing my solution here, based on Chris' answer. Hope it can help others.

I needed to dynamically append child elements into my JSX, but in a simpler way than conditional checks in my return statement. I want to show a loader in the case that the child elements aren't ready yet. Here it is:

export class Settings extends React.PureComponent {
  render() {
    const loading = (<div>I'm Loading</div>);
    let content = [];
    let pushMessages = null;
    let emailMessages = null;

    if (this.props.pushPreferences) {
       pushMessages = (<div>Push Content Here</div>);
    if (this.props.emailPreferences) {
      emailMessages = (<div>Email Content Here</div>);

    // Push the components in the order I want
    if (emailMessages) content.push(emailMessages);
    if (pushMessages) content.push(pushMessages);

    return (
        {content.length ? content : loading}

Now, I do realize I could also just put {pushMessages} and {emailMessages} directly in my return() below, but assuming I had even more conditional content, my return() would just look cluttered.

How can moment.js be imported with typescript?

Still broken? Try uninstalling @types/moment.

So, I removed @types/moment package from the package.json file and it worked using:

import * as moment from 'moment'

Newer versions of moment don't require the @types/moment package as types are already included.

Kotlin - Property initialization using "by lazy" vs. "lateinit"

Additionnally to hotkey's good answer, here is how I choose among the two in practice:

lateinit is for external initialisation: when you need external stuff to initialise your value by calling a method.

e.g. by calling:

private lateinit var value: MyClass

fun init(externalProperties: Any) {
   value = somethingThatDependsOn(externalProperties)

While lazy is when it only uses dependencies internal to your object.

Failed to load ApplicationContext (with annotation)

In my case, I had to do the following while running with Junit5

@SpringBootTest(classes = {abc.class}) @ExtendWith(SpringExtension.class

Here abc.class was the class that was being tested

Maven:Non-resolvable parent POM and 'parent.relativePath' points at wrong local POM

You can try with the following way,


So that the parent jar will be fetching from the repository.

setInterval in a React app

Updated 10-second countdown using Hooks (a new feature proposal that lets you use state and other React features without writing a class. They’re currently in React v16.7.0-alpha).

import React, { useState, useEffect } from 'react';
import ReactDOM from 'react-dom';

const Clock = () => {
    const [currentCount, setCount] = useState(10);
    const timer = () => setCount(currentCount - 1);

        () => {
            if (currentCount <= 0) {
            const id = setInterval(timer, 1000);
            return () => clearInterval(id);

    return <div>{currentCount}</div>;

const App = () => <Clock />;

ReactDOM.render(<App />, document.getElementById('root'));

React native text going off my screen, refusing to wrap. What to do?

Another solution that I found to this issue is by wrapping the Text inside a View. Also set the style of the View to flex: 1.

ReactJS: setTimeout() not working?

setTimeout(() => {
  this.setState({ position: 1 });
}, 3000);

The above would also work because the ES6 arrow function does not change the context of this.

Why Is `Export Default Const` invalid?

Paul's answer is the one you're looking for. However, as a practical matter, I think you may be interested in the pattern I've been using in my own React+Redux apps.

Here's a stripped-down example from one of my routes, showing how you can define your component and export it as default with a single statement:

import React from 'react';
import { connect } from 'react-redux';

@connect((state, props) => ({
    appVersion: state.appVersion
    // other scene props, calculated from app state & route props
export default class SceneName extends React.Component { /* ... */ }

(Note: I use the term "Scene" for the top-level component of any route).

I hope this is helpful. I think it's much cleaner-looking than the conventional connect( mapState, mapDispatch )( BareComponent )

How can I declare a global variable in Angular 2 / Typescript?

I like the solution from @supercobra too. I just would like to improve it slightly. If you export an object which contains all the constants, you could simply use es6 import the module without using require.

I also used Object.freeze to make the properties become true constants. If you are interested in the topic, you could read this post.

// global.ts

 export const GlobalVariable = Object.freeze({
     BASE_API_URL: '',
     //... more of your variables

Refer the module using import.

//anotherfile.ts that refers to global constants
import { GlobalVariable } from './path/global';

export class HeroService {
    private baseApiUrl = GlobalVariable.BASE_API_URL;

    //... more code

Auto-increment on partial primary key with Entity Framework Core

Annotate the property like below

public int ID { get; set; }

To use identity columns for all value-generated properties on a new model, simply place the following in your context's OnModelCreating():


This will create make all keys and other properties which have .ValueGeneratedOnAdd() have Identity by default. You can use ForNpgsqlUseIdentityAlwaysColumns() to have Identity always, and you can also specify identity on a property-by-property basis with UseNpgsqlIdentityColumn() and UseNpgsqlIdentityAlwaysColumn().

postgres efcore value generation

Browser: Identifier X has already been declared

Remember that window is the global namespace. These two lines attempt to declare the same variable:

window.APP = { ... }
const APP = window.APP

The second definition is not allowed in strict mode (enabled with 'use strict' at the top of your file).

To fix the problem, simply remove the const APP = declaration. The variable will still be accessible, as it belongs to the global namespace.

Violation of PRIMARY KEY constraint. Cannot insert duplicate key in object

To prevent inserting a record that exist already. I'd check if the ID value exists in the database. For the example of a Table created with an IDENTITY PRIMARY KEY:

CREATE TABLE [dbo].[Persons] (    
    LastName VARCHAR(40) NOT NULL,
    FirstName VARCHAR(40)

When JANE DOE and JOE BROWN already exist in the database.

INSERT INTO [dbo].[Persons] (FirstName,LastName)
INSERT INTO Persons (FirstName,LastName) 

DATABASE OUTPUT of TABLE [dbo].[Persons] will be:

ID    LastName   FirstName
1     DOE        Jane
2     BROWN      JOE

I'd check if i should update an existing record or insert a new one. As the following JAVA example:

int NewID = 1;
boolean IdAlreadyExist = false;
// Using SQL database connection
// STEP 1: Set property
System.setProperty("", "true");
// STEP 2: Register JDBC driver
// STEP 3: Open a connection
try (Connection conn1 = DriverManager.getConnection(DB_URL, USER,pwd) {
    String Select = "select * from Persons where  ID = " + ID;
    Statement st1 = conn1.createStatement();
    ResultSet rs1 = st1.executeQuery(Select);
    // iterate through the java resultset
    while ( {
        int ID = rs1.getInt("ID");
        if (NewID==ID) {
            IdAlreadyExist = true;

} catch (SQLException e1) {
if (IdAlreadyExist==false) {
    //Insert new record code here
} else {
    //Update existing record code here

Angular2 get clicked element id

When your HTMLElement doesn't have an id, name or class to call,

then use

<input type="text" (click)="selectedInput($event)">

selectedInput(event: MouseEvent) {
   log(event.srcElement) // HTMInputLElement

Unsupported major.minor version 52.0 in my app

unsupported-major-minor-version error can be because of unsupported JDK version. Update JDK, Go to Module Settings and change the JDK path to the new one. In most of the cases, it fixes the error.

Setting the correct PATH for Eclipse

I have resolved this problem by adding or changing variables in environment variables. Go to Win7 -> My Computer - > Properties - > Advanced system settings -> environment Variables

  1. If there is no variable JAVA_HOME, add it with value of variable, with route to folder where your JDK installed, for examle C:\Program Files\Java\jdk-11.0.2
  2. If there is no variable PATH or it have another value, change the value of variable to C:\Program Files\Java\jdk-11.0.2\bin or add variable PATH with this value

Good Luck

Retrieving subfolders names in S3 bucket from boto3

The AWS cli does this (presumably without fetching and iterating through all keys in the bucket) when you run aws s3 ls s3://my-bucket/, so I figured there must be a way using boto3.

It looks like they indeed use Prefix and Delimiter - I was able to write a function that would get me all directories at the root level of a bucket by modifying that code a bit:

def list_folders_in_bucket(bucket):
    paginator = boto3.client('s3').get_paginator('list_objects')
    folders = []
    iterator = paginator.paginate(Bucket=bucket, Prefix='', Delimiter='/', PaginationConfig={'PageSize': None})
    for response_data in iterator:
        prefixes = response_data.get('CommonPrefixes', [])
        for prefix in prefixes:
            prefix_name = prefix['Prefix']
            if prefix_name.endswith('/'):
    return folders

ES6 class variable alternatives

The way I solved this, which is another option (if you have jQuery available), was to Define the fields in an old-school object and then extend the class with that object. I also didn't want to pepper the constructor with assignments, this appeared to be a neat solution.

function MyClassFields(){
    this.createdAt = new Date();

MyClassFields.prototype = {
    id : '',
    type : '',
    title : '',
    createdAt : null,

class MyClass {
    constructor() {
        $.extend(this,new MyClassFields());

-- Update Following Bergi's comment.

No JQuery Version:

class SavedSearch  {
    constructor() {
            id : '',
            type : '',
            title : '',
            createdAt: new Date(),


You still do end up with 'fat' constructor, but at least its all in one class and assigned in one hit.

EDIT #2: I've now gone full circle and am now assigning values in the constructor, e.g.

class SavedSearch  {
    constructor() { = '';
        this.type = '';
        this.title = '';
        this.createdAt = new Date();

Why? Simple really, using the above plus some JSdoc comments, PHPStorm was able to perform code completion on the properties. Assigning all the vars in one hit was nice, but the inability to code complete the properties, imo, isn't worth the (almost certainly minuscule) performance benefit.

Superscript in markdown (Github flavored)?

Comments about previous answers

The universal solution is using the HTML tag <sup>, as suggested in the main answer.
However, the idea behind Markdown is precisely to avoid the use of such tags:
The document should look nice as plain text, not only when rendered.

Another answer proposes using Unicode characters, which makes the document look nice as a plain text document but could reduce compatibility.

Finally, I would like to remember the simplest solution for some documents: the character ^.
Some Markdown implementation (e.g. MacDown in macOS) interprets the caret as an instruction for superscript.

Sin^2 + Cos^2 = 1
Clearly, Stack Overflow does not interpret the caret as a superscript instruction. However, the text is comprehensible, and this is what really matters when using Markdown.

Import mysql DB with XAMPP in command LINE

You may also need to specify the host. From your statement, it looks like you run on Windows. Try this:

mysql -h localhost -u #myusername -p #mypasswd MYBASE
      < c:/user/folderss/myscript.sql


mysql -h localhost -u #myusername -p #mypasswd MYBASE
       < "c:\user\folderss\myscript.sql"

jQuery counter to count up to a target number

You can use the jQuery animate function

// Enter num from and to
$({countNum: 99}).animate({countNum: 1000}, {
  duration: 8000,
  step: function() {
    // What todo on every count
  complete: function() {

UIView with rounded corners and drop shadow?

Well if you don't want to change your nibs and view hierarchy as suggested David C. this method will do it for you. To add rounded corners and shadow to your UIImageView just use this method, for example:

[Utils roundCornersForImageView:myImageView withCornerRadius:6.0 

(!) For performance reasons I don't think it is a good idea to use this code in something like UITableView, since this code changes view hierarchy. So I will suggest to change your nib and add a container view for shadow effect and use Davic C. code.

+ (void)roundCornersForImageView:(UIImageView *)imageView 
withCornerRadius:(float)cornerRadius andShadowOffset:(float)shadowOffset
    const float CORNER_RADIUS = cornerRadius;
    const float BORDER_WIDTH = 1.0; 
    const float SHADOW_OFFSET = shadowOffset;
    const float SHADOW_OPACITY = 0.8;
    const float SHADOW_RADIUS = 3.0;

    //Our old image now is just background image view with shadow
    UIImageView *backgroundImageView = imageView;
    UIView *superView = backgroundImageView.superview;

    //Make wider actual visible rect taking into account shadow
    CGRect oldBackgroundFrame = backgroundImageView.frame;
    CGRect newBackgroundFrame = CGRectMake(oldBackgroundFrame.origin.x, oldBackgroundFrame.origin.y, oldBackgroundFrame.size.width + SHADOW_OFFSET, oldBackgroundFrame.size.height + SHADOW_OFFSET);
    [backgroundImageView removeFromSuperview];
    backgroundImageView.frame = newBackgroundFrame;        

    //Make new UIImageView with rounded corners and put our old image
    CGRect frameForRoundedImageView = CGRectMake(0, 0, oldBackgroundFrame.size.width, oldBackgroundFrame.size.height);
    UIImageView *roundedImageView = [[UIImageView alloc]initWithFrame:frameForRoundedImageView];
    roundedImageView.image = imageView.image;
    [roundedImageView.layer setCornerRadius:CORNER_RADIUS];
    [roundedImageView.layer setBorderColor:[UIColor lightGrayColor].CGColor];        
    [roundedImageView.layer setBorderWidth:BORDER_WIDTH]; 
    [roundedImageView.layer setMasksToBounds:YES];

    //Set shadow preferences
    [backgroundImageView setImage:nil];
    [backgroundImageView.layer setShadowColor:[UIColor blackColor].CGColor];
    [backgroundImageView.layer setShadowOpacity:SHADOW_OPACITY];
    [backgroundImageView.layer setShadowRadius:SHADOW_RADIUS];
    [backgroundImageView.layer setShadowOffset:CGSizeMake(SHADOW_OFFSET, SHADOW_OFFSET)];   

    //Add out two image views back to the view hierarchy.
    [backgroundImageView addSubview:roundedImageView];
    [superView addSubview:backgroundImageView];   

Stretch Image to Fit 100% of Div Height and Width

Or you can put in the CSS,

div#img {
  background-image: url(“file.png");
  color:yellow (this part doesn't matter;

Redirect in Spring MVC

try to change this in your dispatcher-servlet.xml

<!-- Your View Resolver -->
<bean id="viewResolver" class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
    <property name="basenames" value="views" />
    <property name="order" value="1" />
<!-- UrlBasedViewResolver to Handle Redirects & Forward -->
<bean id="urlViewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
    <property name="viewClass" value="org.springframework.web.servlet.view.tiles2.TilesView" />
    <property name="order" value="2" />

What happens is clearly explained here

Python convert set to string and vice versa

Use repr and eval:

>>> s = set([1,2,3])
>>> strs = repr(s)
>>> strs
'set([1, 2, 3])'
>>> eval(strs)
set([1, 2, 3])

Note that eval is not safe if the source of string is unknown, prefer ast.literal_eval for safer conversion:

>>> from ast import literal_eval
>>> s = set([10, 20, 30])
>>> lis = str(list(s))
>>> set(literal_eval(lis))
set([10, 20, 30])

help on repr:

repr(object) -> string
Return the canonical string representation of the object.
For most object types, eval(repr(object)) == object.

Circular dependency in Spring

It just does it. It instantiates a and b, and injects each one into the other (using their setter methods).

What's the problem?

What's the difference between identifying and non-identifying relationships?

Here's a good description:

Relationships between two entities may be classified as being either "identifying" or "non-identifying". Identifying relationships exist when the primary key of the parent entity is included in the primary key of the child entity. On the other hand, a non-identifying relationship exists when the primary key of the parent entity is included in the child entity but not as part of the child entity's primary key. In addition, non-identifying relationships may be further classified as being either "mandatory" or "non-mandatory". A mandatory non-identifying relationship exists when the value in the child table cannot be null. On the other hand, a non-mandatory non-identifying relationship exists when the value in the child table can be null.

Here's a simple example of an identifying relationship:


ParentID (PK, FK to Parent.ID) -- notice PK

Here's a corresponding non-identifying relationship:


ParentID (FK to Parent.ID) -- notice no PK

Installing packages in Sublime Text 2

This recently worked for me. You just need to add to your packages, so that the package manager would be aware of the packages:

  1. Add the Sublime Text 2 Repository to your Synaptic Package Manager:

    sudo add-apt-repository ppa:webupd8team/sublime-text-2
  2. Update

    sudo apt-get update
  3. Install Sublime Text:

    sudo apt-get install sublime-text

Print an integer in binary format in Java

Try this way:

public class Bin {
  public static void main(String[] args) {
    System.out.println(toBinary(0x94, 8));

  public static String toBinary(int a, int bits) {
    if (--bits > 0)
        return toBinary(a>>1, bits)+((a&0x1)==0?"0":"1");
        return (a&0x1)==0?"0":"1";



How can I use xargs to copy files that have spaces and quotes in their names?

The easiest way to do what the original poster wants is to change the delimiter from any whitespace to just the end-of-line character like this:

find whatever ... | xargs -d "\n" cp -t /var/tmp

Regular expression for URL validation (in JavaScript)

Try this regex


It works best for me.

MVC4 StyleBundle not resolving images

Just remember to fix multiple CSS inclusions in a bundle such as:

bundles.Add(new StyleBundle("~/Content/styles/jquery-ui")
    .Include("~/Content/css/path1/somestyle1.css", "~/Content/css/path2/somestyle2.css"));

You cannot just add new CssRewriteUrlTransform() to the end as you can with one CSS file as the method does not support it, so you have to use Include multiple times:

bundles.Add(new StyleBundle("~/Content/styles/jquery-ui")
    .Include("~/Content/css/path1/somestyle1.css", new CssRewriteUrlTransform())
    .Include("~/Content/css/path2/somestyle2.css", new CssRewriteUrlTransform()));

Referring to a table in LaTeX

You must place the label after a caption in order to for label to store the table's number, not the chapter's number.

\begin{tabular}{| p{5cm} | p{5cm} | p{5cm} |}
  -- cut --
\caption{My table}

Table \ref{table:kysymys} on page \pageref{table:kysymys} refers to the ...

What exactly does the Access-Control-Allow-Credentials header do?

By default, CORS does not include cookies on cross-origin requests. This is different from other cross-origin techniques such as JSON-P. JSON-P always includes cookies with the request, and this behavior can lead to a class of vulnerabilities called cross-site request forgery, or CSRF.

In order to reduce the chance of CSRF vulnerabilities in CORS, CORS requires both the server and the client to acknowledge that it is ok to include cookies on requests. Doing this makes cookies an active decision, rather than something that happens passively without any control.

The client code must set the withCredentials property on the XMLHttpRequest to true in order to give permission.

However, this header alone is not enough. The server must respond with the Access-Control-Allow-Credentials header. Responding with this header to true means that the server allows cookies (or other user credentials) to be included on cross-origin requests.

You also need to make sure your browser isn't blocking third-party cookies if you want cross-origin credentialed requests to work.

Note that regardless of whether you are making same-origin or cross-origin requests, you need to protect your site from CSRF (especially if your request includes cookies).

How to convert the ^M linebreak to 'normal' linebreak in a file opened in vim?

use dos2unix utility if the file was created on windows, use mac2unix utility if the file was created on mac. :)

How do I create/edit a Manifest file?

In Visual Studio 2019 WinForm Projects, it is available under

Project Properties -> Application -> View Windows Settings (button)

enter image description here

Downloading jQuery UI CSS from Google's CDN

As Obama says "Yes We Can". Here is the link to it.

You need to use

Google[VERSION NO]/jquery-ui.min.js[VERSION NO]/themes/[THEME NAME]/jquery-ui.min.css

jQuery CDN[VERSION NO]/jquery-ui.min.js[VERSION NO]/themes/[THEME NAME]/jquery-ui.min.css

Microsoft[VERSION NO]/jquery-ui.min.js[VERSION NO]/themes/[THEME NAME]/jquery-ui.min.css

Find theme names here in gallery subtab


But i would not recommend you hosting from cdn for the following reasons

  1. Although your chance of hit rate is good in case of Google CDN compared to others but it's still abysmally low.(any cdn not just google).
  2. Loading via cdn you will have 3 requests one for jQuery.js, one for jQueryUI.js and one for your code. You might as will compress it on your local and load it as one single resource.

How to recompile with -fPIC

After the configure step you probably have a makefile. Inside this makefile look for CFLAGS (or similar). puf -fPIC at the end and run make again. In other words -fPIC is a compiler option that has to be passed to the compiler somewhere.

Use 'import module' or 'from module import'?

There's another detail here, not mentioned, related to writing to a module. Granted this may not be very common, but I've needed it from time to time.

Due to the way references and name binding works in Python, if you want to update some symbol in a module, say, from outside that module, and have other importing code "see" that change, you have to import foo a certain way. For example:

module foo:

bar = "apples"

module a:

import foo = "oranges"   # update bar inside foo module object

module b:

import foo           
print        # if executed after a's "" assignment, will print "oranges"

However, if you import symbol names instead of module names, this will not work.

For example, if I do this in module a:

from foo import bar
bar = "oranges"

No code outside of a will see bar as "oranges" because my setting of bar merely affected the name "bar" inside module a, it did not "reach into" the foo module object and update its "bar".

Can typescript export a function?

If you are using this for Angular, then export a function via a named export. Such as:

function someFunc(){}

export { someFunc as someFuncName }

otherwise, Angular will complain that object is not a function.

How can I avoid running ActiveRecord callbacks?

This solution is Rails 2 only.

I just investigated this and I think I have a solution. There are two ActiveRecord private methods that you can use:


You're going to have to use send to call these methods. examples:

p = => 'foo')

p = Person.find(1)

This is definitely something that you'll only really want to use in the console or while doing some random tests. Hope this helps!

Mockito: Inject real objects into private @Autowired fields

In Spring there is a dedicated utility called ReflectionTestUtils for this purpose. Take the specific instance and inject into the the field.


Foo foo;

void _before(){
   ReflectionTestUtils.setField(foo,"bar", new BarImpl());// `bar` is private field

Authentication versus Authorization

As Authentication vs Authorization puts it:

Authentication is the mechanism whereby systems may securely identify their users. Authentication systems provide an answers to the questions:

  • Who is the user?
  • Is the user really who he/she represents himself to be?

Authorization, by contrast, is the mechanism by which a system determines what level of access a particular authenticated user should have to secured resources controlled by the system. For example, a database management system might be designed so as to provide certain specified individuals with the ability to retrieve information from a database but not the ability to change data stored in the datbase, while giving other individuals the ability to change data. Authorization systems provide answers to the questions:

  • Is user X authorized to access resource R?
  • Is user X authorized to perform operation P?
  • Is user X authorized to perform operation P on resource R?

See also:

How to set radio button selected value using jquery

This is the only syntax that worked for me

$('input[name="assReq"][value="' + obj["AssociationReq"] + '"]').prop('checked', 'checked');

Postgresql 9.2 pg_dump version mismatch

On Ubuntu you can simply add the most recent Apt repository and then run:

sudo apt-get install postgresql-client-11

Query to convert from datetime to date mysql

Either Cybernate or OMG Ponies solution will work. The fundamental problem is that the DATE_FORMAT() function returns a string, not a date. When you wrote

(Select Date_Format(orders.date_purchased,'%m/%d/%Y')) As Date 

I think you were essentially asking MySQL to try to format the values in date_purchased according to that format string, and instead of calling that column date_purchased, call it "Date". But that column would no longer contain a date, it would contain a string. (Because Date_Format() returns a string, not a date.)

I don't think that's what you wanted to do, but that's what you were doing.

Don't confuse how a value looks with what the value is.

Collision Detection between two images in Java

is there a problem with:

Rectangle box1 = new Rectangle(100,100,100,100);
Rectangle box2 = new Rectangle(200,200,100,100);

// what this means is if any pixel in box2 enters (hits) box1
if (box1.contains(box2)) 
     // collision occurred

// your code for moving the boxes 

this can also be applied to circles:

Ellipse2D.Double ball1 = new Ellipse2D.Double(100,100,200,200);
Ellipse2D.Double ball2 = new Ellipse2D.Double(400,100,200,200);

// what this means is if any pixel on the circumference in ball2 touches (hits)
// ball1
    if (ball1.contains(ball2)) 
         // collision occurred

    // your code for moving the balls

to check whether youve hit the edge of a screen you could use the following:

Rectangle screenBounds = jpanel.getBounds();
Ellipse2D.Double ball = new Ellipse2D.Double(100,100,200,200);  // diameter 200
Rectangle ballBounds = ball.getBounds();

if (!screenBounds.contains(ballBounds))
// the ball touched the edge of the screen

Ruby 2.0.0p0 IRB warning: "DL is deprecated, please use Fiddle"

The message you received is common when you have ruby 2.0.0p0 (2013-02-24) on top of Windows.

The message "DL is deprecated, please use Fiddle" is not an error; it's only a warning.

The source is the Deprecation notice for DL introduced some time ago in dl.rb ( see revisions/37910 ).

On Windows the lib/ruby/site_ruby/2.0.0/readline.rb file still requires dl.rb so the warning message comes out when you require 'irb' ( because irb requires 'readline' ) or when anything else wants to require 'readline'.

You can open readline.rb with your favorite text editor and look up the code ( near line 4369 ):

    if RUBY_VERSION < '1.9.1'
      require 'Win32API'
      require 'dl'
      class Win32API
        DLL = {}

We can always hope for an improvement to work out this deprecation in future releases of Ruby.

EDIT: For those wanting to go deeper about Fiddle vs DL, let it be said that their purpose is to dynamically link external libraries with Ruby; you can read on the ruby-doc website about DL or Fiddle.

How to convert a Map to List in Java?

"Map<String , String > map = new HapshMap<String , String>;
 map.add("two" ,"spring");
 Set<Entry<String,String>> set =  map.entrySet();
 List<Entry<String , String>> list = new ArrayList<Entry<String , String>>    (set);
 for(Entry<String , String> entry : list ) {
 } "

Java current machine name and logged in user?

To get the currently logged in user:


To get the host name of the machine:


To answer the last part of your question, the Java API says that getHostName() will return

the host name for this IP address, or if the operation is not allowed by the security check, the textual representation of the IP address.

jQuery-UI datepicker default date

Jquery Datepicker defaultDate ONLY set the default date that you chose on the calendar that pops up when you click on your field. If you want the default date to APPEAR on your input before the user clicks on the field you should give a val() to your field. Something like this:

$("#searchDateFrom").datepicker({ defaultDate: "-1y -1m -6d" });
$("#searchDateFrom").val((date.getMonth()) + '/' + (date.getDate() - 6) + '/' + (date.getFullYear() - 1));

Java Webservice Client (Best way)

Some ideas in the following answer:

Steps in creating a web service using Axis2 - The client code

Gives an example of a Groovy client invoking the ADB classes generated from the WSDL.

There are lots of web service frameworks out there...

How to create an empty file with Ansible?

A combination of two answers, with a twist. The code will be detected as changed, when the file is created or the permission updated.

- name: Touch again the same file, but dont change times this makes the task idempotent
    path: /etc/foo.conf
    state: touch
    mode: 0644
    modification_time: preserve
    access_time: preserve
  changed_when: >
    p.diff.before.state == "absent" or
    p.diff.before.mode|default("0644") != "0644"

and a version that also corrects the owner and group and detects it as changed when it does correct these:

- name: Touch again the same file, but dont change times this makes the task idempotent
    path: /etc/foo.conf
    state: touch
    state: touch
    mode: 0644
    owner: root
    group: root
    modification_time: preserve
    access_time: preserve
  register: p
  changed_when: >
    p.diff.before.state == "absent" or
    p.diff.before.mode|default("0644") != "0644" or
    p.diff.before.owner|default(0) != 0 or|default(0) != 0

What is the meaning of "__attribute__((packed, aligned(4))) "

  • packed means it will use the smallest possible space for struct Ball - i.e. it will cram fields together without padding
  • aligned means each struct Ball will begin on a 4 byte boundary - i.e. for any struct Ball, its address can be divided by 4

These are GCC extensions, not part of any C standard.

Adding click event listener to elements with the same class

I find it more convenient to use something like the following:


    if( != "IMG"){


How do you use colspan and rowspan in HTML tables?

Use rowspan if you want to extend cells down and colspan to extend across.

Forward declaration of a typedef in C++

Like @BillKotsias, I used inheritance, and it worked for me.

I changed this mess (which required all the boost headers in my declaration *.h)

#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/mean.hpp>
#include <boost/accumulators/statistics/moment.hpp>
#include <boost/accumulators/statistics/min.hpp>
#include <boost/accumulators/statistics/max.hpp>

typedef boost::accumulators::accumulator_set<float,
 >> VanillaAccumulator_t ;
std::unique_ptr<VanillaAccumulator_t> acc;

into this declaration (*.h)

class VanillaAccumulator;
std::unique_ptr<VanillaAccumulator> acc;

and the implementation (*.cpp) was

#include <boost/accumulators/accumulators.hpp>
#include <boost/accumulators/statistics.hpp>
#include <boost/accumulators/statistics/stats.hpp>
#include <boost/accumulators/statistics/mean.hpp>
#include <boost/accumulators/statistics/moment.hpp>
#include <boost/accumulators/statistics/min.hpp>
#include <boost/accumulators/statistics/max.hpp>

class VanillaAccumulator : public

JPA Criteria API - How to add JOIN clause (as general sentence as possible)

You don't need to learn JPA. You can use my easy-criteria for JPA2 ( Here is the example

CriteriaComposer<Pet> petCriteria CriteriaComposer.from(Pet.class).
where(Pet_.type, EQUAL, "Cat").join(Pet_.owner).where(,EQUAL, "foo");

List<Pet> result = CriteriaProcessor.findAllEntiry(petCriteria);


List<Tuple> result =  CriteriaProcessor.findAllTuple(petCriteria);

How to register multiple servlets in web.xml in one Spring application

As explained in this thread on the cxf-user mailing list, rather than having the CXFServlet load its own spring context from user-webservice-servlet.xml, you can just load the whole lot into the root context. Rename your existing user-webservice-servlet.xml to some other name (e.g. user-webservice-beans.xml) then change your contextConfigLocation parameter to something like:






HTML input arrays

As far as I know, there isn't anything on the HTML specs because browsers aren't supposed to do anything different for these fields. They just send them as they normally do and PHP is the one that does the parsing into an array, as do other languages.

How to use OAuth2RestTemplate?

In the answer from @mariubog ( I was using password grant types too as in the example but needed to set the client authentication scheme to form. Scopes were not supported by the endpoint for password and there was no need to set the grant type as the ResourceOwnerPasswordResourceDetails object sets this itself in the constructor.


public ResourceOwnerPasswordResourceDetails() {


The key thing for me was the client_id and client_secret were not being added to the form object to post in the body if resource.setClientAuthenticationScheme(AuthenticationScheme.form); was not set.

See the switch in:

Finally, when connecting to Salesforce endpoint the password token needed to be appended to the password.

class MyConfig {

private String tokenUrl;

private String clientId;

private String clientSecret;

private String passwordToken;

private String username;

private String password;

protected OAuth2ProtectedResourceDetails resource() {

    ResourceOwnerPasswordResourceDetails resource = new ResourceOwnerPasswordResourceDetails();

    resource.setPassword(password + passwordToken);

    return resource;

 public OAuth2RestOperations restTemplate() {
    return new OAuth2RestTemplate(resource(), new DefaultOAuth2ClientContext(new DefaultAccessTokenRequest()));

class MyService {
    private OAuth2RestOperations restTemplate;

    public MyService() {

How to install a Mac application using Terminal

Probably not exactly your issue..

Do you have any spaces in your package path? You should wrap it up in double quotes to be safe, otherwise it can be taken as two separate arguments

sudo installer -store -pkg "/User/MyName/Desktop/helloWorld.pkg" -target /

Hibernate Auto Increment ID

If you have a numeric column that you want to auto-increment, it might be an option to set columnDefinition directly. This has the advantage, that the schema auto-generates the value even if it is used without hibernate. This might make your code db-specific though:

import javax.persistence.Column;
@Column(columnDefinition = "serial") // postgresql

psql: FATAL: Peer authentication failed for user "dev"

For people in the future seeing this, postgres is in the /usr/lib/postgresql/10/bin on my Ubuntu server.

I added it to the PATH in my .bashrc file, and add this line at the end


then on the command line

$> source ./.bashrc

I refreshed my bash environment. Now I can use postgres -D /wherever from any directory

Best way to Bulk Insert from a C# DataTable

If using SQL Server, SqlBulkCopy.WriteToServer(DataTable)

Or also with SQL Server, you can write it to a .csv and use BULK INSERT

If using MySQL, you could write it to a .csv and use LOAD DATA INFILE

If using Oracle, you can use the array binding feature of ODP.NET

If SQLite:

nvarchar(max) vs NText

I want to add that you can use the .WRITE clause for partial or full updates and high performance appends to varchar(max)/nvarchar(max) data types.

Here you can found full example of using .WRITE clause.

The remote host closed the connection. The error code is 0x800704CD

I was getting this on an 2.0 iis7 Windows2008 site. Same code on iis6 worked fine. It was causing an issue for me because it was messing up the login process. User would login and get a 302 to default.asxp, which would get through page_load, but not as far as pre-render before iis7 would send a 302 back to login.aspx without the auth cookie. I started playing with app pool settings, and for some reason 'enable 32 bit applications' seems to have fixed it. No idea why, since this site isn't doing anything special that should require any 32 bit drivers. We have some sites that still use Access that require 32bit, but not our straight SQL sites like this one.

What difference is there between WebClient and HTTPWebRequest classes in .NET?

WebClient is a higher-level abstraction built on top of HttpWebRequest to simplify the most common tasks. For instance, if you want to get the content out of an HttpWebResponse, you have to read from the response stream:

var http = (HttpWebRequest)WebRequest.Create("");
var response = http.GetResponse();

var stream = response.GetResponseStream();
var sr = new StreamReader(stream);
var content = sr.ReadToEnd();

With WebClient, you just do DownloadString:

var client = new WebClient();
var content = client.DownloadString("");

Note: I left out the using statements from both examples for brevity. You should definitely take care to dispose your web request objects properly.

In general, WebClient is good for quick and dirty simple requests and HttpWebRequest is good for when you need more control over the entire request.

Unable to Connect to For Cloning

You are probably behind a firewall. Try cloning via https – that has a higher chance of not being blocked:

git clone

Send email with PHPMailer - embed image in body

I found the answer:

$mail->AddEmbeddedImage('img/2u_cs_mini.jpg', 'logo_2u');

and on the <img> tag put src='cid:logo_2u'

Storing JSON in database vs. having a new column for each key

Updated 4 June 2017

Given that this question/answer have gained some popularity, I figured it was worth an update.

When this question was originally posted, MySQL had no support for JSON data types and the support in PostgreSQL was in its infancy. Since 5.7, MySQL now supports a JSON data type (in a binary storage format), and PostgreSQL JSONB has matured significantly. Both products provide performant JSON types that can store arbitrary documents, including support for indexing specific keys of the JSON object.

However, I still stand by my original statement that your default preference, when using a relational database, should still be column-per-value. Relational databases are still built on the assumption of that the data within them will be fairly well normalized. The query planner has better optimization information when looking at columns than when looking at keys in a JSON document. Foreign keys can be created between columns (but not between keys in JSON documents). Importantly: if the majority of your schema is volatile enough to justify using JSON, you might want to at least consider if a relational database is the right choice.

That said, few applications are perfectly relational or document-oriented. Most applications have some mix of both. Here are some examples where I personally have found JSON useful in a relational database:

  • When storing email addresses and phone numbers for a contact, where storing them as values in a JSON array is much easier to manage than multiple separate tables

  • Saving arbitrary key/value user preferences (where the value can be boolean, textual, or numeric, and you don't want to have separate columns for different data types)

  • Storing configuration data that has no defined schema (if you're building Zapier, or IFTTT and need to store configuration data for each integration)

I'm sure there are others as well, but these are just a few quick examples.

Original Answer

If you really want to be able to add as many fields as you want with no limitation (other than an arbitrary document size limit), consider a NoSQL solution such as MongoDB.

For relational databases: use one column per value. Putting a JSON blob in a column makes it virtually impossible to query (and painfully slow when you actually find a query that works).

Relational databases take advantage of data types when indexing, and are intended to be implemented with a normalized structure.

As a side note: this isn't to say you should never store JSON in a relational database. If you're adding true metadata, or if your JSON is describing information that does not need to be queried and is only used for display, it may be overkill to create a separate column for all of the data points.

"while :" vs. "while true"

The colon is a built-in command that does nothing, but returns 0 (success). Thus, it's shorter (and faster) than calling an actual command to do the same thing.

What is the purpose and use of **kwargs?

In Java, you use constructors to overload classes and allow for multiple input parameters. In python, you can use kwargs to provide similar behavior.

java example:

python example:

class Robot():
    # name is an arg and color is a kwarg
    def __init__(self,name, color='red'): = name
        self.color = color

red_robot = Robot('Bob')
blue_robot = Robot('Bob', color='blue')

print("I am a {color} robot named {name}.".format(color=red_robot.color,
print("I am a {color} robot named {name}.".format(color=blue_robot.color,

>>> I am a red robot named Bob.
>>> I am a blue robot named Bob.

just another way to think about it.

Jquery function return value

I'm not entirely sure of the general purpose of the function, but you could always do this:

function getMachine(color, qty) {
    var retval;
    $("#getMachine li").each(function() {
        var thisArray = $(this).text().split("~");
        if(thisArray[0] == color&& qty>= parseInt(thisArray[1]) && qty<= parseInt(thisArray[2])) {
            retval = thisArray[3];
            return false;
    return retval;

var retval = getMachine(color, qty);

Jenkins pipeline how to change to another folder

Use WORKSPACE environment variable to change workspace directory.

If doing using Jenkinsfile, use following code :

    sh "pwd"

How do I read the file content from the Internal storage - Android App

To read a file from internal storage:

Call openFileInput() and pass it the name of the file to read. This returns a FileInputStream. Read bytes from the file with read(). Then close the stream with close().


StringBuilder sb = new StringBuilder();
            BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
            String line = null;
            while ((line = reader.readLine()) != null) {
        } catch(OutOfMemoryError om){
        } catch(Exception ex){
        String result = sb.toString();

Split string and get first value only

Actually, there is a better way to do it than split:

public string GetFirstFromSplit(string input, char delimiter)
    var i = input.IndexOf(delimiter);

    return i == -1 ? input : input.Substring(0, i);

And as extension methods:

public static string FirstFromSplit(this string source, char delimiter)
    var i = source.IndexOf(delimiter);

    return i == -1 ? source : source.Substring(0, i);

public static string FirstFromSplit(this string source, string delimiter)
    var i = source.IndexOf(delimiter);

    return i == -1 ? source : source.Substring(0, i);


string result = "hi, hello, sup".FirstFromSplit(',');
Console.WriteLine(result); // "hi"

Confirm password validation in Angular 6

I found a bug in AJT_82's answer. Since I do not have enough reputation to comment under AJT_82's answer, I have to post the bug and solution in this answer.

Here is the bug:

enter image description here

Solution: In the following code:

export class MyErrorStateMatcher implements ErrorStateMatcher {
  isErrorState(control: FormControl | null, form: FormGroupDirective | NgForm | null): boolean {
    const invalidCtrl = !!(control && control.invalid && control.parent.dirty);
    const invalidParent = !!(control && control.parent && control.parent.invalid && control.parent.dirty);

    return (invalidCtrl || invalidParent);

Change control.parent.invalid to control.parent.hasError('notSame') will solve this problem.

After the small changes, the problem solved.

enter image description here

Edit: To validate the Confirm Password field only after the user starts typing you can return this instead

return ((invalidCtrl || invalidParent) && control.valid);

Fiddler not capturing traffic from browsers

I've had the same problem. The solution was to remove proxy from Chrome settings. Also you could have an extension that use proxy. Try to disable it.

Printing out a linked list using toString

A very simple solution is to override the toString() method in the Node. Then, you can call print by passing LinkedList's head. You don't need to implement any kind of loop.


public class LinkedListNode {

    public String toString() {
        return String.format("Node(%d, next = %s)", data, next);

public class LinkedList {

    public static void main(String[] args) {

        LinkedList l = new LinkedList();


What is the difference between for and foreach?

foreach syntax is quick and easy. for syntax is a little more complex, but is also more flexible.

foreach is useful when iterating all of the items in a collection. for is useful when iterating overall or a subset of items.

The foreach iteration variable which provides each collection item, is READ-ONLY, so we can't modify the items as they are iterated. Using the for syntax, we can modify the items as needed.

Bottom line- use foreach to quickly iterate all of the items in a collection. Use for to iterate a subset of the items of the collection or to modify the items as they are iterated.

T-SQL to list all the user mappings with database roles/permissions for a Login

Is this the kind of thing you want? You might want to extend it to get more info out of the sys tables.

use master

DECLARE @name VARCHAR(50) -- database name 

select name from sys.databases

OPEN db_cursor  
FETCH NEXT FROM db_cursor INTO @name  

       print @name
      exec('USE ' +  @name + '; select, from sys.database_role_members drm
            join sys.database_principals rp on (drm.role_principal_id = rp.principal_id)
            join sys.database_principals mp on (drm.member_principal_id = mp.principal_id)')
       FETCH NEXT FROM db_cursor INTO @name  

CLOSE db_cursor  
DEALLOCATE db_cursor

Force encode from US-ASCII to UTF-8 (iconv)

The following converts all files in a folder.

Create backup folder of original files.

mkdir backup

Convert all files in US ASCII encoding to UTF-8 (single line command)

for f in $(file -i * .sql | grep us-ascii | cut -d ':' -f 1); do iconv -f us-ascii -t utf-8 $f -o $ f.utf-8 && mv $f backup / && mv "$f.utf-8" $f; done

Convert all files in encoding ISO 8859-1 to UTF-8 (single line command)

for f $(file -i * .sql | grep iso-8859-1 | cut -d ':' -f 1); do iconv -f iso-8859-1 -t utf-8 $f -o $f.utf-8 && mv $f backup / && mv "$f.utf-8" $f; done

Output data from all columns in a dataframe in pandas

I know this is an old question, but I have just had a similar problem and I think what I did would work for you too.

I used the to_csv() method and wrote to stdout:

import sys


This should dump the whole dataframe whether it's nicely-printable or not, and you can use the to_csv parameters to configure column separators, whether the index is printed, etc.

Edit: It is now possible to use None as the target for .to_csv() with similar effect, which is arguably a lot nicer:


How to use Session attributes in Spring-mvc

Use @SessionAttributes

See the docs: Using @SessionAttributes to store model attributes in the HTTP session between requests

"Understanding Spring MVC Model And Session Attributes" also gives a very good overview of Spring MVC sessions and explains how/when @ModelAttributes are transferred into the session (if the controller is @SessionAttributes annotated).

That article also explains that it is better to use @SessionAttributes on the model instead of setting attributes directly on the HttpSession because that helps Spring MVC to be view-agnostic.

How to increase dbms_output buffer?

When buffer size gets full. There are several options you can try:

1) Increase the size of the DBMS_OUTPUT buffer to 1,000,000

2) Try filtering the data written to the buffer - possibly there is a loop that writes to DBMS_OUTPUT and you do not need this data.

3) Call ENABLE at various checkpoints within your code. Each call will clear the buffer.

DBMS_OUTPUT.ENABLE(NULL) will default to 20000 for backwards compatibility Oracle documentation on dbms_output

You can also create your custom output display.something like below snippets

create or replace procedure cust_output(input_string in varchar2 )

   out_string_in long default in_string; 
   string_lenth number; 
   loop_count number default 0; 


   str_len := length(out_string_in);

   while loop_count < str_len
      dbms_output.put_line( substr( out_string_in, loop_count +1, 255 ) ); 
      loop_count := loop_count +255; 
   end loop; 

Link -Ref :Alternative to dbms_output.putline @ By: Alexander

Showing ValueError: shapes (1,3) and (1,3) not aligned: 3 (dim 1) != 1 (dim 0)

Unlike standard arithmetic, which desires matching dimensions, dot products require that the dimensions are one of:

  • (X..., A, B) dot (Y..., B, C) -> (X..., Y..., A, C), where ... means "0 or more different values
  • (B,) dot (B, C) -> (C,)
  • (A, B) dot (B,) -> (A,)
  • (B,) dot (B,) -> ()

Your problem is that you are using np.matrix, which is totally unnecessary in your code - the main purpose of np.matrix is to translate a * b into, b). As a general rule, np.matrix is probably not a good choice.

How do I find ' % ' with the LIKE operator in SQL Server?

Try this:

declare @var char(3)
set @var='[%]'
select Address from Accomodation where Address like '%'+@var+'%' 

You must use [] cancels the effect of wildcard, so you read % as a normal character, idem about character _

Save file Javascript with file name

function saveAs(uri, filename) {
    var link = document.createElement('a');
    if (typeof === 'string') {
        document.body.appendChild(link); // Firefox requires the link to be in the body = filename;
        link.href = uri;;
        document.body.removeChild(link); // remove the link when done
    } else {

How to copy text to the client's clipboard using jQuery?

Copying to the clipboard is a tricky task to do in Javascript in terms of browser compatibility. The best way to do it is using a small flash. It will work on every browser. You can check it in this article.

Here's how to do it for Internet Explorer:

function copy (str)
    //for IE ONLY!

Append a Lists Contents to another List C#

Try AddRange-method:


How to disable PHP Error reporting in CodeIgniter?

Here is the typical structure of new Codeigniter project:

- application/
- system/
- user_guide/
- index.php <- this is the file you need to change

I usually use this code in my CI index.php. Just change local_server_name to the name of your local webserver.

With this code you can deploy your site to your production server without changing index.php each time.

// Domain-based environment
if ($_SERVER['SERVER_NAME'] == 'local_server_name') {
    define('ENVIRONMENT', 'development');
} else {
    define('ENVIRONMENT', 'production');

 * Different environments will require different levels of error reporting.
 * By default development will show errors but testing and live will hide them.

if (defined('ENVIRONMENT')) {
    switch (ENVIRONMENT) {
        case 'development':
        case 'testing':
        case 'production':
            ini_set('display_errors', 0);  
            exit('The application environment is not set correctly.');

Parsing GET request parameters in a URL that contains another URL

$get_url = "";
$my_url = "http://localhost/test.php?id=" . urlencode($get_url);

$my_url outputs:


So now you can get this value using $_GET['id'] or $_REQUEST['id'] (decoded).

echo urldecode($_GET["id"]);


To get every GET parameter:

foreach ($_GET as $key=>$value) {
  echo "$key = " . urldecode($value) . "<br />\n";

$key is GET key and $value is GET value for $key.

Or you can use alternative solution to get array of GET params

$get_parameters = array();
if (isset($_SERVER['QUERY_STRING'])) {
  $pairs = explode('&', $_SERVER['QUERY_STRING']);
  foreach($pairs as $pair) {
    $part = explode('=', $pair);
    $get_parameters[$part[0]] = sizeof($part)>1 ? urldecode($part[1]) : "";

$get_parameters is same as url decoded $_GET.

auto refresh for every 5 mins

Auto reload with target of your choice. In this case target is _self set to every 5 minutes.

300000 milliseconds = 300 seconds = 5 minutes

as 60000 milliseconds = 60 seconds = 1 minute.

This is how you do it:

<script type="text/javascript">
function load()
setTimeout("'', '_self');", 300000);
<body onload="load()">

Or this if it is the same page to reload itself:

<script type="text/javascript">
function load()
setTimeout(", '_self');", 300000);
<body onload="load()">

How to implement reCaptcha for ASP.NET MVC?

For anybody else looking, here is a decent set of steps.

Don't forget to manually add your key in OnActionExecuting() like I did.

sudo echo "something" >> /etc/privilegedFile doesn't work

echo 'Hello World' | (sudo tee -a /etc/apt/sources.list)

Microsoft.Office.Core Reference Missing

You need to download and install the PIA (primary interop assemblies) for the version of Office you are using. Once installed you can then add a reference to your project and they will be available from the add reference dialog. Here are the links to download them...

Office 2010 PIA

Office 2007 PIA

Office 2003 PIA

gcc warning" 'will be initialized after'

If you're seeing errors from library headers and you're using GCC, then you can disable warnings by including the headers using -isystem instead of -I.

Similar features exist in clang.

If you're using CMake, you can specify SYSTEM for include_directories.

What is the best/safest way to reinstall Homebrew?

For me, this one worked without the sudo access.

ruby -e "$(curl -fsSL"

For more reference, please follow

enter image description here

How to export JavaScript array info to csv (on client side)?

In Chrome 35 update, download attribute behavior was changed.

to work this in chrome, use this

var pom = document.createElement('a');
var csvContent=csv; //here we load our csv data 
var blob = new Blob([csvContent],{type: 'text/csv;charset=utf-8;'});
var url = URL.createObjectURL(blob);
pom.href = url;
pom.setAttribute('download', 'foo.csv');;

How to load a model from an HDF5 file in Keras?

load_weights only sets the weights of your network. You still need to define its architecture before calling load_weights:

def create_model():
   model = Sequential()
   model.add(Dense(64, input_dim=14, init='uniform'))
   model.add(BatchNormalization(epsilon=1e-06, mode=0, momentum=0.9, weights=None))
   model.add(Dense(64, init='uniform'))
   model.add(BatchNormalization(epsilon=1e-06, mode=0, momentum=0.9, weights=None))
   model.add(Dense(2, init='uniform'))
   return model

def train():
   model = create_model()
   sgd = SGD(lr=0.1, decay=1e-6, momentum=0.9, nesterov=True)
   model.compile(loss='binary_crossentropy', optimizer=sgd)

   checkpointer = ModelCheckpoint(filepath="/tmp/weights.hdf5", verbose=1, save_best_only=True), y_train, nb_epoch=20, batch_size=16, show_accuracy=True, validation_split=0.2, verbose=2, callbacks=[checkpointer])

def load_trained_model(weights_path):
   model = create_model()

How do I set the time zone of MySQL?

I thought this might be useful:

There are three places where the timezone might be set in MySQL:

In the file "my.cnf" in the [mysqld] section


@@global.time_zone variable

To see what value they are set to:

SELECT @@global.time_zone;

To set a value for it use either one:

SET GLOBAL time_zone = '+8:00';
SET GLOBAL time_zone = 'Europe/Helsinki';
SET @@global.time_zone = '+00:00';

(Using named timezones like 'Europe/Helsinki' means that you have to have a timezone table properly populated.)

Keep in mind that +02:00 is an offset. Europe/Berlin is a timezone (that has two offsets) and CEST is a clock time that corresponds to a specific offset.

@@session.time_zone variable

SELECT @@session.time_zone;

To set it use either one:

SET time_zone = 'Europe/Helsinki';
SET time_zone = "+00:00";
SET @@session.time_zone = "+00:00";

Both might return SYSTEM which means that they use the timezone set in my.cnf.

For timezone names to work, you must setup your timezone information tables need to be populated: I also mention how to populate those tables in this answer.

To get the current timezone offset as TIME


It will return 02:00:00 if your timezone is +2:00.

To get the current UNIX timestamp:


To get the timestamp column as a UNIX timestamp

SELECT UNIX_TIMESTAMP(`timestamp`) FROM `table_name`

To get a UTC datetime column as a UNIX timestamp

SELECT UNIX_TIMESTAMP(CONVERT_TZ(`utc_datetime`, '+00:00', @@session.time_zone)) FROM `table_name`

Note: Changing the timezone will not change the stored datetime or timestamp, but it will show a different datetime for existing timestamp columns as they are internally stored as UTC timestamps and externally displayed in the current MySQL timezone.

I made a cheatsheet here: Should MySQL have its timezone set to UTC?

How to convert java.sql.timestamp to LocalDate (java8) java.time?

The accepted answer is not ideal, so I decided to add my 2 cents


is a bad solution in general, I'm not even sure why they added this method to the JDK as it makes things really confusing by doing an implicit conversion using the system timezone. Usually when using only java8 date classes the programmer is forced to specify a timezone which is a good thing.

The good solution is


Where zoneId is the timezone you want to use which is typically either ZoneId.systemDefault() if you want to use your system timezone or some hardcoded timezone like ZoneOffset.UTC

The general approach should be

  1. Break free to the new java8 date classes using a class that is directly related, e.g. in our case java.time.Instant is directly related to java.sql.Timestamp, i.e. no timezone conversions are needed between them.
  2. Use the well-designed methods in this java8 class to do the right thing. In our case atZone(zoneId) made it explicit that we are doing a conversion and using a particular timezone for it.

Is there a way to use two CSS3 box shadows on one element?

Box shadows can use commas to have multiple effects, just like with background images (in CSS3).

How can I write an anonymous function in Java?

With the introduction of lambda expression in Java 8 you can now have anonymous methods.

Say I have a class Alpha and I want to filter Alphas on a specific condition. To do this you can use a Predicate<Alpha>. This is a functional interface which has a method test that accepts an Alpha and returns a boolean.

Assuming that the filter method has this signature:

List<Alpha> filter(Predicate<Alpha> filterPredicate)

With the old anonymous class solution you would need to something like:

filter(new Predicate<Alpha>() {
   boolean test(Alpha alpha) {
      return alpha.centauri > 1;

With the Java 8 lambdas you can do:

filter(alpha -> alpha.centauri > 1);

For more detailed information see the Lambda Expressions tutorial

How to show Page Loading div until the page has finished loading?

for drupal in your theme custom_theme.theme file

function custom_theme_preprocess_html(&$variables) {
$variables['preloader'] = 1;

In html.html.twig file after skip main content link in body

{% if preloader %} 
  <div id="test-preloader" >
    <div id="preloader-inner" class="cssload-container">
      <div class="wait-text">{{ 'Please wait...'|t }} </div> 
      <div class="cssload-item cssload-moon"></div>
{% endif %}  

in css file

#test-preloader {
position: fixed;
background: white;
width: 100%;
height: 100%;
top: 0;
left: 0;
z-index: 9999;
.cssload-container .wait-text {
text-align: center;
padding-bottom: 15px;
color: #000;

.cssload-container .cssload-item {
 margin: auto;
 position: absolute;
 top: 0;
 right: 0;
 bottom: 0;
 left: 0;
 width: 131px;
 height: 131px;
 background-color: #fff;
 box-sizing: border-box;
 -o-box-sizing: border-box;
 -ms-box-sizing: border-box;
 -webkit-box-sizing: border-box;
 -moz-box-sizing: border-box;
 box-shadow: 0 0 21px 3px rgba(130, 130, 130, 0.26);
 -o-box-shadow: 0 0 21px 3px rgba(130, 130, 130, 0.26);
 -ms-box-shadow: 0 0 21px 3px rgba(130, 130, 130, 0.26);
 -webkit-box-shadow: 0 0 21px 3px rgba(130, 130, 130, 0.26);
 -moz-box-shadow: 0 0 21px 3px rgba(130, 130, 130, 0.26);

.cssload-container .cssload-moon {
border-bottom: 26px solid #008AFA;
border-radius: 50%;
-o-border-radius: 50%;
-ms-border-radius: 50%;
-webkit-border-radius: 50%;
-moz-border-radius: 50%;
animation: spin 1.45s ease infinite;
-o-animation: spin 1.45s ease infinite;
-ms-animation: spin 1.45s ease infinite;
-webkit-animation: spin 1.45s ease infinite;
-moz-animation: spin 1.45s ease infinite;

Script parameters in Bash

In bash $1 is the first argument passed to the script, $2 second and so on

/usr/local/bin/abbyyocr9 -rl Swedish -if "$1" -of "$2" 2>&1

So you can use:

./ some_source_file.png destination_file.txt

Explanation on double quotes;

consider three scripts:

bash $1

# cat
bash "$1"

echo "1-$1" "2-$2"

Now invoke:

$ bash "a b"
1-a 2-b

$ bash "a b"
1-a b 2-

When you invoke "a b" then it invokes a b (two arguments), and with "a b" it invokes "a b" (1 argument). Always have in mind how parameters are passed and expaned in bash, it will save you a lot of headache.

Adding additional data to select options using jQuery

To store another value in select options:

$("#select").append('<option value="4">another</option>')

How to download folder from putty using ssh client

You need to use some kind of file-transfer protocol (ftp, scp, etc), putty can't send remote files back to your computer. I use Win-SCP, which has a straightforward gui. Select SCP and you should be able to log in with the same ssh credentials and on the same port (probably 22) that you use with putty.

How to remove white space characters from a string in SQL Server

There may be 2 spaces after the text, please confirm. You can use LTRIM and RTRIM functions also right?


Maybe the extra space isn't ordinary spaces (ASCII 32, soft space)? Maybe they are "hard space", ASCII 160?

ltrim(rtrim(replace(ProductAlternateKey, char(160), char(32))))

Can you use Microsoft Entity Framework with Oracle?

The answer is "mostly".

We've hit a problem using it where the EF generates code that uses the CROSS and OUTER APPLY operators. This link shows that MS knows its a problem with SQL Server previous to 2005 however, they forget to mention that these operators are not supported by Oracle either.

How to use if-else option in JSTL

you have to use this code:

with <%@ taglib prefix="c" uri=""%>


            <option value="RCV"
                ${records[0].getDirection() == 'RCV' ? 'selected="true"' : ''}>
                <spring:message code="dropdown.Incoming" text="dropdown.Incoming" />
            <option value="SND"
                ${records[0].getDirection() == 'SND'? 'selected="true"' : ''}>
                <spring:message code="dropdown.Outgoing" text="dropdown.Outgoing" />

Check if an array contains duplicate values

Late answer but can be helpful

function areThereDuplicates(args) {

    let count = {};
    for(let i = 0; i < args.length; i++){
         count[args[i]] = 1 + (count[args[i]] || 0);
    let found = Object.keys(count).filter(function(key) {
        return count[key] > 1;
    return found.length ? true : false; 


JSP tricks to make templating easier?

Use tiles. It saved my life.

But if you can't, there's the include tag, making it similar to php.

The body tag might not actually do what you need it to, unless you have super simple content. The body tag is used to define the body of a specified element. Take a look at this example:

<jsp:element name="${content.headerName}"   
   <jsp:attribute name="lang">${content.lang}</jsp:attribute>   

You specify the element name, any attributes that element might have ("lang" in this case), and then the text that goes in it--the body. So if

  • content.headerName = h1,
  • content.lang = fr, and
  • content.body = Heading in French

Then the output would be

<h1 lang="fr">Heading in French</h1>

What is the use of the @Temporal annotation in Hibernate?

I use Hibernate 5.2 and @Temporal is not required anymore.,, time.LocalDate are stored into DB with appropriate datatype as Date/timestamp.

What good are SQL Server schemas?

development - each of our devs get their own schema as a sandbox to play in.

What is the equivalent to getch() & getche() in Linux?

I suggest you use curses.h or ncurses.h these implement keyboard management routines including getch(). You have several options to change the behavior of getch (i.e. wait for keypress or not).

Update multiple values in a single statement

If your DB supports it, concatenating all 3 updates into one sql string will save on server-round-trips if querying over the LAN. So if nothing else works, this might give you a slight improvement. The typical 'multi-statement delimiter is the semi-colon, eg:

'update x....;update y...;update...z'

In Python, when to use a Dictionary, List or Set?

A list keeps order, dict and set don't: when you care about order, therefore, you must use list (if your choice of containers is limited to these three, of course;-).

dict associates with each key a value, while list and set just contain values: very different use cases, obviously.

set requires items to be hashable, list doesn't: if you have non-hashable items, therefore, you cannot use set and must instead use list.

set forbids duplicates, list does not: also a crucial distinction. (A "multiset", which maps duplicates into a different count for items present more than once, can be found in collections.Counter -- you could build one as a dict, if for some weird reason you couldn't import collections, or, in pre-2.7 Python as a collections.defaultdict(int), using the items as keys and the associated value as the count).

Checking for membership of a value in a set (or dict, for keys) is blazingly fast (taking about a constant, short time), while in a list it takes time proportional to the list's length in the average and worst cases. So, if you have hashable items, don't care either way about order or duplicates, and want speedy membership checking, set is better than list.

Char Comparison in C

I believe you are trying to compare two strings representing values, the function you are looking for is:

int atoi(const char *nptr);


long int strtol(const char *nptr, char **endptr, int base);

these functions will allow you to convert a string to an int/long int:

int val = strtol("555", NULL, 10);

and compare it to another value.

int main (int argc, char *argv[])
    long int val = 0;
    if (argc < 2)
        fprintf(stderr, "Usage: %s number\n", argv[0]);

    val = strtol(argv[1], NULL, 10);
    printf("%d is %s than 555\n", val, val > 555 ? "bigger" : "smaller");

    return 0;

how to set start page in webconfig file in c#

the following code worked fine for me. kindly check other setting in your web config

                <clear />               
                <add value="Login.aspx"/>

Make child div stretch across width of page

With current browsers (this question is dating a bit now), you can use the much simpler vw (viewport width) unit:

#help_panel {
  margin-left: calc(50% - 50vw);
  width: 100vw;

(usage data:

From my tests, this should not break your flow while being easy to use.

How to create a function in a cshtml template?

why not just declare that function inside the cshtml file?

    public string GetSomeString(){
        return string.Empty;


Docker - a way to give access to a host USB or serial device?

I wanted to extend the answers already given to include support for dynamically connected devices that aren't captured with /dev/bus/usb and how to get this working when using a Windows host along with the boot2docker VM.

If you are working with Windows, you'll need to add any USB rules for devices that you want Docker to access within the VirtualBox manager. To do this you can stop the VM by running:

host:~$ docker-machine stop default

Open the VirtualBox Manager and add USB support with filters as required.

Start the boot2docker VM:

host:~$ docker-machine start default

Since the USB devices are connected to the boot2docker VM, the commands need to be run from that machine. Open up a terminal with the VM and run the docker run command:

host:~$ docker-machine ssh
docker@default:~$ docker run -it --privileged ubuntu bash

Note, when the command is run like this, then only previously connected USB devices will be captures. The volumes flag is only required if you want this to work with devices connected after the container is started. In that case, you can use:

docker@default:~$ docker run -it --privileged -v /dev:/dev ubuntu bash

Note, I had to use /dev instead of /dev/bus/usb in some cases to capture a device like /dev/sg2. I can only assume the same would be true for devices like /dev/ttyACM0 or /dev/ttyUSB0.

The docker run commands will work with a Linux host as well.

jQuery: Test if checkbox is NOT checked

You can also use either jQuery .not() method or :not() selector:

if ($('#checkSurfaceEnvironment').not(':checked').length) {
    // do stuff for not selected

JSFiddle Example

Additional Notes

From the jQuery API documentation for the :not() selector:

The .not() method will end up providing you with more readable selections than pushing complex selectors or variables into a :not() selector filter. In most cases, it is a better choice.

JavaScript: Difference between .forEach() and .map()

The main difference that you need to know is .map() returns a new array while .forEach() doesn't. That is why you see that difference in the output. .forEach() just operates on every value in the array.

Read up:

You might also want to check out: - Array.prototype.every() - JavaScript | MDN

How to get the filename without the extension from a path in Python?

A multiple extension aware procedure. Works for str and unicode paths. Works in Python 2 and 3.

import os

def file_base_name(file_name):
    if '.' in file_name:
        separator_index = file_name.index('.')
        base_name = file_name[:separator_index]
        return base_name
        return file_name

def path_base_name(path):
    file_name = os.path.basename(path)
    return file_base_name(file_name)


>>> path_base_name('file')
>>> path_base_name(u'file')
>>> path_base_name('file.txt')
>>> path_base_name(u'file.txt')
>>> path_base_name('file.tar.gz')
>>> path_base_name('file.a.b.c.d.e.f.g')
>>> path_base_name('relative/path/file.ext')
>>> path_base_name('/absolute/path/file.ext')
>>> path_base_name('Relative\\Windows\\Path\\file.txt')
>>> path_base_name('C:\\Absolute\\Windows\\Path\\file.txt')
>>> path_base_name('/path with spaces/file.ext')
>>> path_base_name('C:\\Windows Path With Spaces\\file.txt')
>>> path_base_name('some/path/file name with')
'file name with spaces'

Map implementation with duplicate keys

class  DuplicateMap<K, V> 
    enum MapType

    int HashCode = 0;
    Map<Key<K>,V> map = null;

        map = new HashMap<Key<K>,V>();

    DuplicateMap( MapType maptype )
        if ( maptype == MapType.Hash ) {
            map = new HashMap<Key<K>,V>();
        else if ( maptype == MapType.LinkedHash ) {
            map = new LinkedHashMap<Key<K>,V>();
            map = new HashMap<Key<K>,V>();

    V put( K key, V value  )

        return map.put( new Key<K>( key , HashCode++ ), value );

    void putAll( Map<K, V> map1 )
        Map<Key<K>,V> map2 = new LinkedHashMap<Key<K>,V>();

        for ( Entry<K, V> entry : map1.entrySet() ) {
            map2.put( new Key<K>( entry.getKey() , HashCode++ ), entry.getValue());

    Set<Entry<K, V>> entrySet()
        Set<Entry<K, V>> entry = new LinkedHashSet<Map.Entry<K,V>>();
        for ( final Entry<Key<K>, V> entry1 : map.entrySet() ) {
            entry.add( new Entry<K, V>(){
                private K Key = entry1.getKey().Key();
                private V Value = entry1.getValue();

                public K getKey() {
                    return Key;

                public V getValue() {
                    return Value;

                public V setValue(V value) {
                    return null;

        return entry;

    public String toString() {
        StringBuilder builder = new  StringBuilder();
        boolean FirstIteration = true;
        for ( Entry<K, V> entry : entrySet() ) {
            builder.append( ( (FirstIteration)? "" : "," ) + ((entry.getKey()==null) ? null :entry.getKey().toString() ) + "=" + ((entry.getValue()==null) ? null :entry.getValue().toString() )  );
            FirstIteration = false;
        return builder.toString();

    class Key<K1>
        K1 Key;
        int HashCode;

        public Key(K1 key, int hashCode) {
            Key = key;
            HashCode = hashCode;

        public K1 Key() {
            return Key;

        public String toString() {
            return  Key.toString() ;

        public int hashCode() {

            return HashCode;

SQLAlchemy insert or update example

assuming certain column names...


newToner = Toner(toner_id = 1,
                    toner_color = 'blue',
                    toner_hex = '#0F85FF')


INSERT multiple

newToner1 = Toner(toner_id = 1,
                    toner_color = 'blue',
                    toner_hex = '#0F85FF')

newToner2 = Toner(toner_id = 2,
                    toner_color = 'red',
                    toner_hex = '#F01731')

dbsession.add_all([newToner1, newToner2])   


q = dbsession.query(Toner)
q = q.filter(Toner.toner_id==1)
record =
record.toner_color = 'Azure Radiance'


or using a fancy one-liner using MERGE

record = dbsession.merge(Toner( **kwargs))

cURL not working (Error #77) for SSL connections on CentOS for non-root users

I had faced same issue whenever I tried executing curl on my https server.

About to connect() to localhost port 443 (#0)
Trying ::1...
Connected to localhost (::1) port 443 (#0)
Initializing NSS with certpath: sql:/etc/pki/nssdb

Observed this issue when I configured keystore path incorrectly. After correcting keystore path it worked.

How to create a testflight invitation code?

after you add the user for testing. the user should get an email. open that email by your iOS device, then click "Start testing" it will bring you to testFlight to download the app directly. If you open that email via computer, and then click "Start testing" it will show you another page which have the instruction of how to install the app. and that invitation code is on the last line. those All upper case letters is the code.

Force drop mysql bypassing foreign key constraint

Drop database exist in all versions of MySQL. But if you want to keep the table structure, here is an idea

mysqldump --no-data --add-drop-database --add-drop-table -hHOSTNAME -uUSERNAME -p > dump.sql

This is a program, not a mysql command

Then, log into mysql and

source dump.sql;

Run a script in Dockerfile

WORKDIR /scripts
RUN ./ 

How to convert 2D float numpy array to 2D int numpy array?

If you're not sure your input is going to be a Numpy array, you can use asarray with dtype=int instead of astype:

>>> np.asarray([1,2,3,4], dtype=int)
array([1, 2, 3, 4])

If the input array already has the correct dtype, asarray avoids the array copy while astype does not (unless you specify copy=False):

>>> a = np.array([1,2,3,4])
>>> a is np.asarray(a)  # no copy :)
>>> a is a.astype(int)  # copy :(
>>> a is a.astype(int, copy=False)  # no copy :)

Python progression path - From apprentice to guru

Not precisely what you're asking for, but I think it's good advice.

Learn another language, doesn't matter too much which. Each language has it's own ideas and conventions that you can learn from. Learn about the differences in the languages and more importantly why they're different. Try a purely functional language like Haskell and see some of the benefits (and challenges) of functions free of side-effects. See how you can apply some of the things you learn from other languages to Python.

How to increase the execution timeout in php?

I know you are specifically asking about the PHP timeout, but what no one else seems to have mentioned is that there can also be a timeout on the webserver and it can look very similar to the PHP timeout.

So if you have tried:

  1. Increasing the timeout in php.ini by adding a line: max_execution_time = {number of seconds i.e. 60 for one minute}
  2. Increasing the timeout in your script itself by adding: ini_set('max_execution_time','{number of seconds i.e. 60 for one minute}');

And you have checked with the phpinfo() function that max_execution_time has indeed be increased, then you might want to try adding this to .htaccess which will make sure Apache itself does not time out:

RewriteRule .* - [E=noabort:1]
RewriteRule .* - [E=noconntimeout:1]

More info here:

Subtract two dates in SQL and get days of the result




DATEDIFF() returns (expr1 – expr2) expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

@D Stanley

Exit a Script On Error

If you put set -e in a script, the script will terminate as soon as any command inside it fails (i.e. as soon as any command returns a nonzero status). This doesn't let you write your own message, but often the failing command's own messages are enough.

The advantage of this approach is that it's automatic: you don't run the risk of forgetting to deal with an error case.

Commands whose status is tested by a conditional (such as if, && or ||) do not terminate the script (otherwise the conditional would be pointless). An idiom for the occasional command whose failure doesn't matter is command-that-may-fail || true. You can also turn set -e off for a part of the script with set +e.

How do I use JDK 7 on Mac OSX?

I know that some may want to smack me for re-opening old post, but if you feel so do it I just hope this may help someone else trying to set JDK 7 on Mac OS (using IntelliJ).

What I did to get this working on my machine is to:

  • followed instructions on Oracle JDK7 Mac OS X Port for general installation
  • in IntelliJ open/create new project so you can add new SDK (File > Project Structure)
  • select Platform Settings > SDKs, press "+" (plus) sign to add new SDK
  • select JSDK and navigate to /Library/Java/JavaVirtualMachines/JDK 1.7.0 Developer Preview.jdk/Contents/Home. Do not get it mistaken with /Users/YOUR_USERNAME/Library/Java/. This will link 4 JARs from "lib" directory (dt.jar, jconsole.jar, sa-jdi.jar and tools.jar)
  • you will need also add JARs from /Library/Java/JavaVirtualMachines/JDK 1.7.0 Developer Preview.jdk/Contents/Home/jre/lib (charsets.jar, jce.jar, JObjC.jar, jsse.jar, management-agent.jar, resources.jar and rt.jar)

What's the difference between next() and nextLine() methods from Scanner class?

  • Just for another example of and nextLine() is that like below : nextLine() does not let user type while next() makes Scanner wait and read the input.

     Scanner sc = new Scanner(;
     do {
        System.out.println("The values on dice are :");
        for(int i = 0; i < n; i++) {
            System.out.println(ran.nextInt(6) + 1);
        System.out.println("Continue : yes or no");
     } while("yes"));
    // while(sc.nextLine().equals("yes"));

Android BroadcastReceiver within Activity

 Toast.makeText(getApplicationContext(), "received", Toast.LENGTH_SHORT);

makes the toast, but doesnt show it.

You have to do Toast.makeText(getApplicationContext(), "received", Toast.LENGTH_SHORT).show();

Hot deploy on JBoss - how do I make JBoss "see" the change?

Deploy the app as exploded (project.war folder), add in your web.xml:


Update the web.xml time every-time you deploy (append blank line):

set PRJ_HOME=C:\Temp2\MyProject\src\main\webapp
set PRJ_CLSS_HOME=%PRJ_HOME%\WEB-INF\classes\com\myProject

set JBOSS_HOME= C:\Java\jboss-4.2.3.GA-jdk6\server\default\deploy\MyProject.war
set JBOSS_CLSS_HOME= %JBOSS_HOME%\WEB-INF\classes\com\myProject

copy %PRJ_CLSS_HOME%\frontend\actions\profile\ProfileAction.class %JBOSS_CLSS_HOME%\frontend\actions\profile\ProfileAction.class
copy %PRJ_CLSS_HOME%\frontend\actions\profile\AjaxAction.class %JBOSS_CLSS_HOME%\frontend\actions\profile\AjaxAction.class


android: how to use getApplication and getApplicationContext from non activity / service class

Sending your activity context to other classes could cause memoryleaks because holding that context alive is the reason that the GC can't dispose the object

Is there a Wikipedia API?

MediaWiki's API is running on Wikipedia (docs). You can also use the Special:Export feature to dump data and parse it yourself.

More information.

A project with an Output Type of Class Library cannot be started directly

If you convert the WPF application to Class library for get the projects .dll file.After that convert the same project to the WPF application you get the following error.

Error:".exe does not contain a static main method suitable for an entry point".

Steps to troubleshoot: 1.Include the App.xaml file in the respective project. 2.Right Click on App.xaml file change the build action to Application Definition 3.Now Build your project

Calculate median in c#

CenterSpace's NMath library provides a function:

double[] values = new double[arraySize];
double median = NMathFunctions.Median(values);

Optionally you can opt to use NaNMedian (if your array may contain null values) but you will need to convert the array to a vector:

double median = NMathFunctions.NaNMedian(new DoubleVector(values));

CenterSpace's NMath Library isn't free, but many universities have licenses

Get file content from URL?

Use file_get_contents in combination with json_decode and echo.

What are some reasons for jquery .focus() not working?

Only "keyboard focusable" elements can be focused with .focus(). div aren't meant to be natively focusable. You have to add tabindex="0" attributes to it to achieve that. input, button, a etc... are natively focusable.

Update rows in one table with data from another table based on one column in each being equal

You Could always use and leave out the "when not matched section"

merge into table1 FromTable   
   using table2 ToTable
     on     ( FromTable.field1 = ToTable.field1
          and  FromTable.field2 =ToTable.field2)
when Matched then
update set 
  ToTable.fieldr = FromTable.fieldx,
  ToTable.fields = FromTable.fieldy, 
  ToTable.fieldt =  FromTable.fieldz)
when not matched then
  insert  (ToTable.field1,
  values (FromTable.field1,

How to convert int to QString?

In it's simplest form, use the answer of Georg Fritzsche

For a bit advanced, you can use this,

QString QString::arg ( int a, int fieldWidth = 0, int base = 10, const QChar & fillChar = QLatin1Char( ' ' ) ) const

Get the documentation and an example here..

Is there a difference between /\s/g and /\s+/g?

\s means "one space", and \s+ means "one or more spaces".

But, because you're using the /g flag (replace all occurrences) and replacing with the empty string, your two expressions have the same effect.

Call a "local" function within module.exports from another function in module.exports?

To fix your issue, i have made few changes in bla.js and it is working,

var foo= function (req, res, next) {
  console.log('inside foo');
  return ("foo");

var  bar= function(req, res, next) {;
module.exports = {bar,foo};

and no modification in app.js

var bla = require('./bla.js');

Git Bash is extremely slow on Windows 7 x64

I solved my slow Git problem on Windows 7 x64 by starting cmd.exe with "Run as administrator".

Python Write bytes to file

If you want to write bytes then you should open the file in binary mode.

f = open('/tmp/output', 'wb')

Instantiating a generic type

You cannot do new T() due to type erasure. The default constructor can only be

public Navigation() {     this("", "", null); } 

​ You can create other constructors to provide default values for trigger and description. You need an concrete object of T.

Why are my PHP files showing as plain text?

You'll need to add this to your server configuration:

AddType application/x-httpd-php .php

That is assuming you have installed PHP properly, which may not be the case since it doesn't work where it normally would immediately after installing.

It is entirely possible that you'll also have to add the php .so/.dll file to your Apache configuration using a LoadModule directive (usually in httpd.conf).

Add a reference column migration in Rails 4

[Using Rails 5]

Generate migration:

rails generate migration add_user_reference_to_uploads user:references

This will create the migration file:

class AddUserReferenceToUploads < ActiveRecord::Migration[5.1]
  def change
    add_reference :uploads, :user, foreign_key: true

Now if you observe the schema file, you will see that the uploads table contains a new field. Something like: t.bigint "user_id" or t.integer "user_id".

Migrate database:

rails db:migrate

How To Raise Property Changed events on a Dependency Property?

I think the OP is asking the wrong question. The code below will show that it not necessary to manually raise the PropertyChanged EVENT from a dependency property to achieve the desired result. The way to do it is handle the PropertyChanged CALLBACK on the dependency property and set values for other dependency properties there. The following is a working example. In the code below, MyControl has two dependency properties - ActiveTabInt and ActiveTabString. When the user clicks the button on the host (MainWindow), ActiveTabString is modified. The PropertyChanged CALLBACK on the dependency property sets the value of ActiveTabInt. The PropertyChanged EVENT is not manually raised by MyControl.


/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window, INotifyPropertyChanged
    public MainWindow()
        DataContext = this;
        ActiveTabString = "zero";

    private string _ActiveTabString;
    public string ActiveTabString
        get { return _ActiveTabString; }
            if (_ActiveTabString != value)
                _ActiveTabString = value;

    private int _ActiveTabInt;
    public int ActiveTabInt
        get { return _ActiveTabInt; }
            if (_ActiveTabInt != value)
                _ActiveTabInt = value;

    #region INotifyPropertyChanged implementation
    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propertyName)
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));

    private void Button_Click(object sender, RoutedEventArgs e)
        ActiveTabString = (ActiveTabString == "zero") ? "one" : "zero";


public class MyControl : Control
    public static List<string> Indexmap = new List<string>(new string[] { "zero", "one" });

    public string ActiveTabString
        get { return (string)GetValue(ActiveTabStringProperty); }
        set { SetValue(ActiveTabStringProperty, value); }

    public static readonly DependencyProperty ActiveTabStringProperty = DependencyProperty.Register(
        typeof(MyControl), new FrameworkPropertyMetadata(

    public int ActiveTabInt
        get { return (int)GetValue(ActiveTabIntProperty); }
        set { SetValue(ActiveTabIntProperty, value); }
    public static readonly DependencyProperty ActiveTabIntProperty = DependencyProperty.Register(
        typeof(MyControl), new FrameworkPropertyMetadata(
            new Int32(),

    static MyControl()
        DefaultStyleKeyProperty.OverrideMetadata(typeof(MyControl), new FrameworkPropertyMetadata(typeof(MyControl)));


    public override void OnApplyTemplate()

    private static void ActiveTabStringChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        MyControl thiscontrol = sender as MyControl;

        if (Indexmap[thiscontrol.ActiveTabInt] != thiscontrol.ActiveTabString)
            thiscontrol.ActiveTabInt = Indexmap.IndexOf(e.NewValue.ToString());



    <StackPanel Orientation="Vertical">
    <Button Content="Change Tab Index" Click="Button_Click" Width="110" Height="30"></Button>
    <local:MyControl x:Name="myControl" ActiveTabInt="{Binding ActiveTabInt, Mode=TwoWay}" ActiveTabString="{Binding ActiveTabString}"></local:MyControl>


<Style TargetType="local:MyControl">
        <Setter Property="Template">
                <ControlTemplate TargetType="local:MyControl">
                    <TabControl SelectedIndex="{Binding ActiveTabInt, Mode=TwoWay}">
                        <TabItem Header="Tab Zero">
                            <TextBlock Text="{Binding ActiveTabInt}"></TextBlock>
                        <TabItem Header="Tab One">
                            <TextBlock Text="{Binding ActiveTabInt}"></TextBlock>

Non-invocable member cannot be used like a method?

It have happened because you are trying to use the property "OffenceBox.Text" like a method. Try to remove parenteses from OffenceBox.Text() and it'll work fine.

Remember that you cannot create a method and a property with the same name in a class.

By the way, some alias could confuse you, since sometimes it's method or property, e.g: "Count" alias:

Namespace: System.Linq

using System.Linq

namespace Teste
    public class TestLinq
        public return Foo()
            var listX = new List<int>();
            return listX.Count(x => x.Id == 1);

Namespace: System.Collections.Generic

using System.Collections.Generic

namespace Teste
    public class TestList
        public int Foo()
            var listX = new List<int>();
            return listX.Count;

Are there inline functions in java?

What you said above is correct. Sometimes final methods are created as inline, but there is no other way to explicitly create an inline function in java.

How to check if directory exist using C++ and winAPI

0.1 second Google search:

BOOL DirectoryExists(const char* dirName) {
  DWORD attribs = ::GetFileAttributesA(dirName);
  if (attribs == INVALID_FILE_ATTRIBUTES) {
    return false;
  return (attribs & FILE_ATTRIBUTE_DIRECTORY);

Format cell if cell contains date less than today


Returns true for dates up to and including today, false otherwise.

How to indent/format a selection of code in Visual Studio Code with Ctrl + Shift + F

(This works at least up to version 1.52.0, 10 Dec 2020)

On macOS Visual Studio Code version 1.36.1 (2019)

Visual Studio Code version 1.36.1 (2019)

To auto-format the selection, use ?K ?F (the trick is that this is to be done in sequence, ?K first, followed by ?F).

Auto-format selection or document

To just indent (shift right) without auto-formatting, use ?]

Indent options

As in Keyboard Shortcuts (?K ?S, or from the menu as shown below)

Keyboard shortcuts

git repo says it's up-to-date after pull but files are not updated

Try this:

 git fetch --all
 git reset --hard origin/master


git fetch downloads the latest from remote without trying to merge or rebase anything.

Please let me know if you have any questions!

Install shows error in console: INSTALL FAILED CONFLICTING PROVIDER

If you have different flavors and you want to avoid collisions in the authority name you can add an applicationIdSuffix to build types and use the resulting applicationId in your manifest, like this:


Is it possible to simulate key press events programmatically?

Building on the answer from alex2k8, here's a revised version that works in all browsers that jQuery supports (the problem was in missing arguments to jQuery.event.trigger, which is easy to forget when using that internal function).

// jQuery plugin. Called on a jQuery object, not directly.
jQuery.fn.simulateKeyPress = function (character) {
  // Internally calls jQuery.event.trigger with arguments (Event, data, elem).
  // That last argument, 'elem', is very important!
  jQuery(this).trigger({ type: 'keypress', which: character.charCodeAt(0) });

jQuery(function ($) {
  // Bind event handler
  $('body').keypress(function (e) {
  // Simulate the key press

You could even push this further and let it not only simulate the event but actually insert the character (if it is an input element), however there are many cross-browser gotcha's when trying to do that. Better use a more elaborate plugin like SendKeys.

The meaning of NoInitialContextException error

The javax.naming package comprises the JNDI API. Since it's just an API, rather than an implementation, you need to tell it which implementation of JNDI to use. The implementations are typically specific to the server you're trying to talk to.

To specify an implementation, you pass in a Properties object when you construct the InitialContext. These properties specify the implementation to use, as well as the location of the server. The default InitialContext constructor is only useful when there are system properties present, but the properties are the same as if you passed them in manually.

As to which properties you need to set, that depends on your server. You need to hunt those settings down and plug them in.

How to get MD5 sum of a string using python?

You can do the following:

Python 2.x

import hashlib
print hashlib.md5("whatever your string is").hexdigest()

Python 3.x

import hashlib
print(hashlib.md5("whatever your string is".encode('utf-8')).hexdigest())

However in this case you're probably better off using this helpful Python module for interacting with the Flickr API:

... which will deal with the authentication for you.

Official documentation of hashlib

Cheap way to search a large text file for a string

I've had a go at putting together a multiprocessing example of file text searching. This is my first effort at using the multiprocessing module; and I'm a python n00b. Comments quite welcome. I'll have to wait until at work to test on really big files. It should be faster on multi core systems than single core searching. Bleagh! How do I stop the processes once the text has been found and reliably report line number?

import multiprocessing, os, time
NUMBER_OF_PROCESSES = multiprocessing.cpu_count()

def FindText( host, file_name, text):
    file_size = os.stat(file_name ).st_size 
    m1 = open(file_name, "r")

    #work out file size to divide up to farm out line counting

    chunk = (file_size / NUMBER_OF_PROCESSES ) + 1
    lines = 0
    line_found_at = -1

    seekStart = chunk * (host)
    seekEnd = chunk * (host+1)
    if seekEnd > file_size:
        seekEnd = file_size

    if host > 0: seekStart )

    line = m1.readline()

    while len(line) > 0:
        lines += 1
        if text in line:
            #found the line
            line_found_at = lines
        if m1.tell() > seekEnd or len(line) == 0:
        line = m1.readline()
    return host,lines,line_found_at

# Function run by worker processes
def worker(input, output):
    for host,file_name,text in iter(input.get, 'STOP'):
        output.put(FindText( host,file_name,text ))

def main(file_name,text):
    t_start = time.time()
    # Create queues
    task_queue = multiprocessing.Queue()
    done_queue = multiprocessing.Queue()
    #submit file to open and text to find
    print 'Starting', NUMBER_OF_PROCESSES, 'searching workers'
    for h in range( NUMBER_OF_PROCESSES ):
        t = (h,file_name,text)

    #Start worker processes
    for _i in range(NUMBER_OF_PROCESSES):
        multiprocessing.Process(target=worker, args=(task_queue, done_queue)).start()

    # Get and print results

    results = {}
    for _i in range(NUMBER_OF_PROCESSES):
        host,lines,line_found = done_queue.get()
        results[host] = (lines,line_found)

    # Tell child processes to stop
    for _i in range(NUMBER_OF_PROCESSES):
#        print "Stopping Process #%s" % i

    total_lines = 0
    for h in range(NUMBER_OF_PROCESSES):
        if results[h][1] > -1:
            print text, 'Found at', total_lines + results[h][1], 'in', time.time() - t_start, 'seconds'
        total_lines += results[h][0]

if __name__ == "__main__":
    main( file_name = 'testFile.txt', text = 'IPI1520' )

How can I find the number of elements in an array?

If you have your array in scope you can use sizeof to determine its size in bytes and use the division to calculate the number of elements:

#define NUM_OF_ELEMS 10
int arr[NUM_OF_ELEMS];
size_t NumberOfElements = sizeof(arr)/sizeof(arr[0]);

If you receive an array as a function argument or allocate an array in heap you can not determine its size using the sizeof. You'll have to store/pass the size information somehow to be able to use it:

void DoSomethingWithArray(int* arr, int NumOfElems)
    for(int i = 0; i < NumOfElems; ++i) {
        arr[i] = /*...*/

Batch file script to zip files

This is link by Tomas has a well written script to zip contents of a folder.

To make it work just copy the script into a batch file and execute it by specifying the folder to be zipped(source).

No need to mention destination directory as it is defaulted in the script to Desktop ("%USERPROFILE%\Desktop")

Copying the script here, just incase the web-link is down:


SET sourceDirPath=%1
IF [%2] EQU [] (
  SET destinationDirPath="%USERPROFILE%\Desktop"
) ELSE (
  SET destinationDirPath="%2"
IF [%3] EQU [] (
  SET destinationFileName=""
) ELSE (
  SET destinationFileName="%3"
SET tempFilePath=%TEMP%\FilesToZip.txt
TYPE NUL > %tempFilePath%

FOR /F "DELIMS=*" %%i IN ('DIR /B /S /A-D "%sourceDirPath%"') DO (
  SET filePath=%%i
  SET dirPath=%%~dpi
  SET dirPath=!dirPath:~0,-1!
  SET dirPath=!dirPath:%sourceDirPath%=!
  SET dirPath=!dirPath:%sourceDirPath%=!
  ECHO .SET DestinationDir=!dirPath! >> %tempFilePath%
  ECHO "!filePath!" >> %tempFilePath%

MAKECAB /D MaxDiskSize=0 /D CompressionType=MSZIP /D Cabinet=ON /D Compress=ON /D UniqueFiles=OFF /D DiskDirectoryTemplate=%destinationDirPath% /D CabinetNameTemplate=%destinationFileName%  /F %tempFilePath% > NUL 2>&1

DEL setup.inf > NUL 2>&1
DEL setup.rpt > NUL 2>&1
DEL %tempFilePath% > NUL 2>&1

Can you get the column names from a SqlDataReader?

It is easier to achieve it in SQL


Basic HTTP authentication with Node and Express 4

function auth (req, res, next) {
  var authHeader = req.headers.authorization;
  if (!authHeader) {
      var err = new Error('You are not authenticated!');
      res.setHeader('WWW-Authenticate', 'Basic');
      err.status = 401;
  var auth = new Buffer.from(authHeader.split(' ')[1], 'base64').toString().split(':');
  var user = auth[0];
  var pass = auth[1];
  if (user == 'admin' && pass == 'password') {
      next(); // authorized
  } else {
      var err = new Error('You are not authenticated!');
      res.setHeader('WWW-Authenticate', 'Basic');      
      err.status = 401;

Excel - Sum column if condition is met by checking other column in same table

SUMIF didn't worked for me, had to use SUMIFS.


TableAmount is the table to sum the values, TableMonth the table where we search the condition and January, of course, the condition to meet.

Hope this can help someone!

Creating an array of objects in Java

Here is the clear example of creating array of 10 employee objects, with a constructor that takes parameter:

public class MainClass
    public static void main(String args[])
        System.out.println("Hello, World!");
        //step1 : first create array of 10 elements that holds object addresses.
        Emp[] employees = new Emp[10];
        //step2 : now create objects in a loop.
        for(int i=0; i<employees.length; i++){
            employees[i] = new Emp(i+1);//this will call constructor.

class Emp{
    int eno;
    public Emp(int no){
        eno = no;
        System.out.println("emp constructor called..eno is.."+eno);

Convert character to ASCII code in JavaScript

You can enter a character and get Ascii Code Using this Code

For Example Enter a Character Like A You Get Ascii Code 65

function myFunction(){_x000D_
    var str=document.getElementById("id1");_x000D_
    if (str.value=="") {_x000D_
    var a="ASCII Code is == >  ";_x000D_
document.getElementById("demo").innerHTML =a+str.value.charCodeAt(0);_x000D_
<p>Check ASCII code</p>_x000D_
  Enter any character:  _x000D_
  <input type="text" id="id1" name="text1" maxLength="1"> </br>_x000D_
<button onclick="myFunction()">Get ASCII code</button>_x000D_
<p id="demo" style="color:red;"></p>

How do you Change a Package's Log Level using Log4j?

This work for my:

Also can try:

Ruby String to Date Conversion

You can try

Find date in structure:

text = "get car from repair 2015-02-02 23:00:10"
dates_from_string =

=> ["2015-02-02 23:00:10"]

ASP.NET Setting width of DataBound column in GridView

Width can be set to specific column as below: By percentages:

<asp:BoundField HeaderText="UserInfo"  DataField="UserInfo"  
SortExpression="UserInfo" ItemStyle-Width="100%"></asp:BoundField>


By pixel:

<asp:BoundField HeaderText="UserInfo"  DataField="UserInfo"  
SortExpression="UserInfo" ItemStyle-Width="500px"></asp:BoundField>

How to build and run Maven projects after importing into Eclipse IDE

When you add dependency in pom.xml , do a maven clean , and then maven build , it will add the jars into you project.

You can search dependency artifacts at

And if it doesn't add jars it should give you errors which will mean that it is not able to fetch the jar, that could be due to broken repository or connection problems.

Well sometimes if it is one or two jars, better download them and add to build path , but with a lot of dependencies use maven.

Why do I get "Pickle - EOFError: Ran out of input" reading an empty file?

if path.exists(Score_file):
      try : 
         with open(Score_file , "rb") as prev_Scr:

            return Unpickler(prev_Scr).load()

    except EOFError : 

        return dict() 

What is the difference between a database and a data warehouse?

Data Warehouse vs Database: A data warehouse is specially designed for data analytics, which involves reading large amounts of data to understand relationships and trends across the data. A database is used to capture and store data, such as recording details of a transaction.

Data Warehouse: Suitable workloads - Analytics, reporting, big data. Data source - Data collected and normalized from many sources. Data capture - Bulk write operations typically on a predetermined batch schedule. Data normalization - Denormalized schemas, such as the Star schema or Snowflake schema. Data storage - Optimized for simplicity of access and high-speed query. performance using columnar storage. Data access - Optimized to minimize I/O and maximize data throughput.

Transactional Database: Suitable workloads - Transaction processing. Data source - Data captured as-is from a single source, such as a transactional system. Data capture - Optimized for continuous write operations as new data is available to maximize transaction throughput. Data normalization - Highly normalized, static schemas. Data storage - Optimized for high throughout write operations to a single row-oriented physical block. Data access - High volumes of small read operations.

Efficient way to remove ALL whitespace from String?

I have found different results to be true. I am trying to replace all whitespace with a single space and the regex was extremely slow.

return( Regex::Replace( text, L"\s+", L" " ) );

What worked the most optimally for me (in C++ cli) was:

String^ ReduceWhitespace( String^ text )
  String^ newText;
  bool    inWhitespace = false;
  Int32   posStart = 0;
  Int32   pos      = 0;
  for( pos = 0; pos < text->Length; ++pos )
    wchar_t cc = text[pos];
    if( Char::IsWhiteSpace( cc ) )
      if( !inWhitespace )
        if( pos > posStart ) newText += text->Substring( posStart, pos - posStart );
        inWhitespace = true;
        newText += L' ';
      posStart = pos + 1;
      if( inWhitespace )
        inWhitespace = false;
        posStart = pos;

  if( pos > posStart ) newText += text->Substring( posStart, pos - posStart );

  return( newText );

I tried the above routine first by replacing each character separately, but had to switch to doing substrings for the non-space sections. When applying to a 1,200,000 character string:

  • the above routine gets it done in 25 seconds
  • the above routine + separate character replacement in 95 seconds
  • the regex aborted after 15 minutes.

What is a plain English explanation of "Big O" notation?

Big O describes the fundamental scaling nature of an algorithm.

There is a lot of information that Big O does not tell you about a given algorithm. It cuts to the bone and gives only information about the scaling nature of an algorithm, specifically how the resource use (think time or memory) of an algorithm scales in response to the "input size".

Consider the difference between a steam engine and a rocket. They are not merely different varieties of the same thing (as, say, a Prius engine vs. a Lamborghini engine) but they are dramatically different kinds of propulsion systems, at their core. A steam engine may be faster than a toy rocket, but no steam piston engine will be able to achieve the speeds of an orbital launch vehicle. This is because these systems have different scaling characteristics with regards to the relation of fuel required ("resource usage") to reach a given speed ("input size").

Why is this so important? Because software deals with problems that may differ in size by factors up to a trillion. Consider that for a moment. The ratio between the speed necessary to travel to the Moon and human walking speed is less than 10,000:1, and that is absolutely tiny compared to the range in input sizes software may face. And because software may face an astronomical range in input sizes there is the potential for the Big O complexity of an algorithm, it's fundamental scaling nature, to trump any implementation details.

Consider the canonical sorting example. Bubble-sort is O(n2) while merge-sort is O(n log n). Let's say you have two sorting applications, application A which uses bubble-sort and application B which uses merge-sort, and let's say that for input sizes of around 30 elements application A is 1,000x faster than application B at sorting. If you never have to sort much more than 30 elements then it's obvious that you should prefer application A, as it is much faster at these input sizes. However, if you find that you may have to sort ten million items then what you'd expect is that application B actually ends up being thousands of times faster than application A in this case, entirely due to the way each algorithm scales.

For div to extend full height

Did you remember setting the height of the html and body tags in your CSS? This is generally how I've gotten DIVs to extend to full height:

    <style type="text/css">

      html,body { height: 100%; margin: 0px; padding: 0px; }
      #full { background: #0f0; height: 100% }

    <div id="full">

Formatting floats without trailing zeros

You can achieve that in most pythonic way like that:



Add common prefix to all cells in Excel

Select the cell you want to be like this, Go To Cell Properties (or CTRL 1) under Number tab in custom enter "X"#

CSS media query to target only iOS devices

I don't know about targeting iOS as a whole, but to target iOS Safari specifically:

@supports (-webkit-touch-callout: none) {
   /* CSS specific to iOS devices */ 

@supports not (-webkit-touch-callout: none) {
   /* CSS for other than iOS devices */ 

Apparently as of iOS 13 -webkit-overflow-scrolling no longer responds to @supports, but -webkit-touch-callout still does. Of course that could change in the future...

How to get character array from a string?

The spread Syntax

You can use the spread syntax, an Array Initializer introduced in ECMAScript 2015 (ES6) standard:

var arr = [...str];


function a() {_x000D_
    return arguments;_x000D_
var str = 'Hello World';_x000D_
var arr1 = [...str],_x000D_
    arr2 = [...'Hello World'],_x000D_
    arr3 = new Array(...str),_x000D_
    arr4 = a(...str);_x000D_
console.log(arr1, arr2, arr3, arr4);

The first three result in:

["H", "e", "l", "l", "o", " ", "W", "o", "r", "l", "d"]

The last one results in

{0: "H", 1: "e", 2: "l", 3: "l", 4: "o", 5: " ", 6: "W", 7: "o", 8: "r", 9: "l", 10: "d"}

Browser Support

Check the ECMAScript ES6 compatibility table.

Further reading

spread is also referenced as "splat" (e.g. in PHP or Ruby or as "scatter" (e.g. in Python).


Try before buy

Default SecurityProtocol in .NET 4.5

You can override the default behavior in following registry:

Key  : HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319 
Value: SchUseStrongCrypto
Data : 1


Key  : HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.0.30319
Value: SchUseStrongCrypto
Data : 1

For details, please see the implementation of ServicePointManager.

When do Java generics require <? extends T> instead of <T> and is there any downside of switching?

It boils down to:

Class<? extends Serializable> c1 = null;
Class<java.util.Date> d1 = null;
c1 = d1; // compiles
d1 = c1; // wont compile - would require cast to Date

You can see the Class reference c1 could contain a Long instance (since the underlying object at a given time could have been List<Long>), but obviously cannot be cast to a Date since there is no guarantee that the "unknown" class was Date. It is not typsesafe, so the compiler disallows it.

However, if we introduce some other object, say List (in your example this object is Matcher), then the following becomes true:

List<Class<? extends Serializable>> l1 = null;
List<Class<java.util.Date>> l2 = null;
l1 = l2; // wont compile
l2 = l1; // wont compile

...However, if the type of the List becomes ? extends T instead of T....

List<? extends Class<? extends Serializable>> l1 = null;
List<? extends Class<java.util.Date>> l2 = null;
l1 = l2; // compiles
l2 = l1; // won't compile

I think by changing Matcher<T> to Matcher<? extends T>, you are basically introducing the scenario similar to assigning l1 = l2;

It's still very confusing having nested wildcards, but hopefully that makes sense as to why it helps to understand generics by looking at how you can assign generic references to each other. It's also further confusing since the compiler is inferring the type of T when you make the function call (you are not explicitly telling it was T is).

Docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock


This worked for me !

Example docker-compose:

version: "3"
    image: jenkinsci/blueocean
    privileged: true
      - "8080:8080"
      - $HOME/learning/jenkins/jenkins_home:/var/jenkins_home
      - DOCKER_HOST=tcp://socat:2375
      - socat

     image: bpack/socat
     command: TCP4-LISTEN:2375,fork,reuseaddr UNIX-CONNECT:/var/run/docker.sock
        - /var/run/docker.sock:/var/run/docker.sock
        - "2375"

Run java jar file on a server as background process

Run in background and add logs to log file using the following:

nohup java -jar /web/server.jar > log.log 2>&1 &

Convert iterator to pointer?

A safe version to convert an iterator to a pointer (exactly what that means regardless of the implications) and by safe I mean no worries about having to dereference the iterator and cause possible exceptions / errors due to end() / other situations

#include <iostream>
#include <vector>
#include <string.h>

int main()
    std::vector<int> vec;

    char itPtr[25];
    long long itPtrDec;
    std::vector<int>::iterator it = vec.begin();
    memset(&itPtr, 0, 25);
    sprintf(itPtr, "%llu", it);
    itPtrDec = atoll(itPtr);
    printf("it = 0x%X\n", itPtrDec);
    it = vec.begin();
    memset(&itPtr, 0, 25);
    sprintf(itPtr, "%llu", it);
    itPtrDec = atoll(itPtr);
    printf("it = 0x%X\n", itPtrDec);

will print something like

it = 0x0

it = 0x2202E10

It's an incredibly hacky way to do it, but if you need it, it does the job. You will receive some compiler warnings which, if really bothering you, can be removed with #pragma

write multiple lines in a file in python

It can be done like this as well:

target.write(line1 + "\n" + line2 + "\n" + line3 + "\n")

Android: I lost my android key store, what should I do?

You can create a new keystore, but the Android Market wont allow you to upload the apk as an update - worse still, if you try uploading the apk as a new app it will not allow it either as it knows there is a 'different' version of the same apk already in the market even if you delete your previous version from the market

Do your absolute best to find that keystore!!

When you find it, email it to yourself so you have a copy on your gmail that you can go and get in the case you loose it from your hard drive!

Keyboard shortcut to clear cell output in Jupyter notebook

I just looked and found cell|all output|clear which worked with:

Server Information: You are using Jupyter notebook.

The version of the notebook server is: 6.1.5 The server is running on this version of Python: Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)]

Current Kernel Information: Python 3.8.3 (tags/v3.8.3:6f8c832, May 13 2020, 22:37:02) [MSC v.1924 64 bit (AMD64)] Type 'copyright', 'credits' or 'license' for more information IPython 7.19.0 -- An enhanced Interactive Python. Type '?' for help.

JQuery Find #ID, RemoveClass and AddClass

Try this




How do I find the index of a character in a string in Ruby?

index(substring [, offset]) ? fixnum or nil
index(regexp [, offset]) ? fixnum or nil

Returns the index of the first occurrence of the given substring or pattern (regexp) in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to begin the search.

"hello".index('e')             #=> 1
"hello".index('lo')            #=> 3
"hello".index('a')             #=> nil
"hello".index(?e)              #=> 1
"hello".index(/[aeiou]/, -3)   #=> 4

Check out ruby documents for more information.

How can I get a JavaScript stack trace when I throw an exception?

A good (and simple) solution as pointed out in the comments on the original question is to use the stack property of an Error object like so:

function stackTrace() {
    var err = new Error();
    return err.stack;

This will generate output like this:


Giving the name of the calling function along with the URL and line number, its calling function, and so on.

I have a really elaborate and pretty solution that I have devised for a project I am currently working on and I have extracted and reworked it a bit to be generalized. Here it is:

    // Only global namespace.
    var Console = {
        settings: {
            debug: {
                alwaysShowURL: false,
                enabled: true,
                showInfo: true
            stackTrace: {
                enabled: true,
                collapsed: true,
                ignoreDebugFuncs: true,
                spacing: false

    // String formatting prototype function.
    if (!String.prototype.format) {
        String.prototype.format = function () {
            var s = this.toString(),
                args = typeof arguments[0],
                args = (("string" == args || "number" == args) ? arguments : arguments[0]);
            if (!arguments.length)
                return s;
            for (arg in args)
                s = s.replace(RegExp("\\{" + arg + "\\}", "gi"), args[arg]);
            return s;

    // String repeating prototype function.
    if (!String.prototype.times) {
        String.prototype.times = function () {
            var s = this.toString(),
                tempStr = "",
                times = arguments[0];
            if (!arguments.length)
                return s;
            for (var i = 0; i < times; i++)
                tempStr += s;
            return tempStr;

    // Commonly used functions
    Console.debug = function () {
        if (Console.settings.debug.enabled) {
            var args = ((typeof arguments !== 'undefined') ?, 0) : []),
                sUA = navigator.userAgent,
                currentBrowser = {
                    firefox: /firefox/gi.test(sUA),
                    webkit: /webkit/gi.test(sUA),
                aLines = Console.stackTrace().split("\n"),
                iCurrIndex = ((currentBrowser.webkit) ? 3 : 2),
                sCssBlack = "color:black;",
                sCssFormat = "color:{0}; font-weight:bold;",
                sLines = "";

            if (currentBrowser.firefox)
                aCurrentLine = aLines[iCurrIndex].replace(/(.*):/, "$1@").split("@");
            else if (currentBrowser.webkit)
                aCurrentLine = aLines[iCurrIndex].replace("at ", "").replace(")", "").replace(/( \()/gi, "@").replace(/(.*):(\d*):(\d*)/, "$1@$2@$3").split("@");

            // Show info if the setting is true and there's no extra trace (would be kind of pointless).
            if (Console.settings.debug.showInfo && !Console.settings.stackTrace.enabled) {
                var sFunc = aCurrentLine[0].trim(),
                    sURL = aCurrentLine[1].trim(),
                    sURL = ((!Console.settings.debug.alwaysShowURL && context.location.href == sURL) ? "this page" : sURL),
                    sLine = aCurrentLine[2].trim(),

                if (currentBrowser.webkit)
                    sCol = aCurrentLine[3].trim();

      "%cOn line %c{0}%c{1}%c{2}%c of %c{3}%c inside the %c{4}%c function:".format(sLine, ((currentBrowser.webkit) ? ", column " : ""), ((currentBrowser.webkit) ? sCol : ""), sURL, sFunc),
                             sCssBlack, sCssFormat.format("red"),
                             sCssBlack, sCssFormat.format("purple"),
                             sCssBlack, sCssFormat.format("green"),
                             sCssBlack, sCssFormat.format("blue"),

            // If the setting permits, get rid of the two obvious debug functions (Console.debug and Console.stackTrace).
            if (Console.settings.stackTrace.ignoreDebugFuncs) {
                // In WebKit (Chrome at least), there's an extra line at the top that says "Error" so adjust for this.
                if (currentBrowser.webkit)

            sLines = aLines.join(((Console.settings.stackTrace.spacing) ? "\n\n" : "\n")).trim();

            trace = typeof trace !== 'undefined' ? trace : true;
            if (typeof console !== "undefined") {
                for (var arg in args)

                if (Console.settings.stackTrace.enabled) {
                    var sCss = "color:red; font-weight: bold;",
                        sTitle = "%c Stack Trace" + " ".times(70);

                    if (Console.settings.stackTrace.collapsed)
                        console.groupCollapsed(sTitle, sCss);
              , sCss);

                    console.debug("%c" + sLines, "color: #666666; font-style: italic;");

    Console.stackTrace = function () {
        var err = new Error();
        return err.stack;

    context.Console = Console;

Check it out on GitHub (currently v1.2)! You can use it like Console.debug("Whatever"); and it will, depending on the settings in Console, print the output and a stack trace (or just simple info/nothing extra at all). Here's an example:


Make sure to play around with the settings in the Console object! You can add spacing between the lines of the trace and turn it off entirely. Here it is with Console.trace set to false:

No trace

You can even turn off the first bit of info shown (set Console.settings.debug.showInfo to false) or disable debugging entirely (set Console.settings.debug.enabled to false) so you never have to comment out a debug statement again! Just leave them in and this will do nothing.

Databinding an enum property to a ComboBox in WPF


    public enum RULE
        [Description( "?????, ??? ???????????" )]
        [Description( "????? ???? ????? ??? ? ???" )]
        [Description( "????????, ??? ???????????" )]
        [Description( "???????? ???? ????? ??? ? ???" )]

    class ExtendRULE
        public static object Values
                List<object> list = new List<object>();
                foreach( RULE rule in Enum.GetValues( typeof( RULE ) ) )
                    string desc = rule.GetType().GetMember( rule.ToString() )[0].GetCustomAttribute<DescriptionAttribute>().Description;
                    list.Add( new { value = rule, desc = desc } );
                return list;


   <ListBox ItemsSource= "{Binding Source={x:Static model:ExtendRULE.Values}}" DisplayMemberPath="desc" SelectedValuePath="value" SelectedValue="{Binding SelectedRule}"/>
   <ComboBox ItemsSource="{Binding Source={x:Static model:ExtendRULE.Values}}" DisplayMemberPath="desc" SelectedValuePath="value" SelectedValue="{Binding SelectedRule}"/>                        

Switch in Laravel 5 - Blade

You can just add these code in AppServiceProvider class boot method.

Blade::extend(function($value, $compiler){
        $value = preg_replace('/(\s*)@switch\((.*)\)(?=\s)/', '$1<?php switch($2):', $value);
        $value = preg_replace('/(\s*)@endswitch(?=\s)/', '$1endswitch; ?>', $value);
        $value = preg_replace('/(\s*)@case\((.*)\)(?=\s)/', '$1case $2: ?>', $value);
        $value = preg_replace('/(?<=\s)@default(?=\s)/', 'default: ?>', $value);
        $value = preg_replace('/(?<=\s)@breakswitch(?=\s)/', '<?php break;', $value);
        return $value;

then you can use as:

@switch( $item )
    @case( condition_1 )
        // do something
    @case( condition_2 )
        // do something else
        // do default behaviour

Enjoy It~

How do I replicate a \t tab space in HTML?

You must use

<dd> </dd> in the html code.

<dd>A free, open source, cross-platform,graphical web browser developed by theMozilla Corporation and hundreds of volunteers.</dd>

    A free, open source, cross-platform, graphical web browser developed by the Mozilla 
    Corporation and hundreds of volunteers.

enter image description here

Ternary operation in CoffeeScript

You may also write it in two statements if it mostly is true use:

a = 5
a = 10 if false

Or use a switch statement if you need more possibilities:

a = switch x
  when true then 5
  when false then 10

With a boolean it may be oversized but i find it very readable.

How to send redirect to JSP page in Servlet

Look at the HttpServletResponse#sendRedirect(String location) method.

Use it as:

response.sendRedirect(request.getContextPath() + "/welcome.jsp")

Alternatively, look at HttpServletResponse#setHeader(String name, String value) method.

The redirection is set by adding the location header:

response.setHeader("Location", request.getContextPath() + "/welcome.jsp");

Sending an HTTP POST request on iOS

The following code describes a simple example using POST method.(How one can pass data by POST method)

Here, I describe how one can use of POST method.

1. Set post string with actual username and password.

NSString *post = [NSString stringWithFormat:@"Username=%@&Password=%@",@"username",@"password"]; 

2. Encode the post string using NSASCIIStringEncoding and also the post string you need to send in NSData format.

NSData *postData = [post dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; 

You need to send the actual length of your data. Calculate the length of the post string.

NSString *postLength = [NSString stringWithFormat:@"%d",[postData length]]; 

3. Create a Urlrequest with all the properties like HTTP method, http header field with length of the post string. Create URLRequest object and initialize it.

NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init]; 

Set the Url for which your going to send the data to that request.

[request setURL:[NSURL URLWithString:@""]]; 

Now, set HTTP method (POST or GET). Write this lines as it is in your code.

[request setHTTPMethod:@"POST"]; 

Set HTTP header field with length of the post data.

[request setValue:postLength forHTTPHeaderField:@"Content-Length"]; 

Also set the Encoded value for HTTP header Field.

[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];

Set the HTTPBody of the urlrequest with postData.

[request setHTTPBody:postData];

4. Now, create URLConnection object. Initialize it with the URLRequest.

NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self]; 

It returns the initialized url connection and begins to load the data for the url request. You can check that whether you URL connection is done properly or not using just if/else statement as below.

if(conn) {
    NSLog(@"Connection Successful");
} else {
    NSLog(@"Connection could not be made");

5. To receive the data from the HTTP request , you can use the delegate methods provided by the URLConnection Class Reference. Delegate methods are as below.

// This method is used to receive the data which we get using post method.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData*)data

// This method receives the error report in case of connection is not made to server. 
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error 

// This method is used to process the data after connection has made successfully.
- (void)connectionDidFinishLoading:(NSURLConnection *)connection

Also Refer This and This documentation for POST method.

And here is best example with source code of HTTPPost Method.

Error: could not find function ... in R

I got the same, error, I was running version .99xxx, I checked for updates from help menu and updated My RStudio to 1.0x, then the error did not come

So simple solution, just update your R Studio

How can I initialize base class member variables in derived class constructor?

If you don't specify visibility for a class member, it defaults to "private". You should make your members private or protected if you want to access them in a subclass.

Woocommerce get products

Do not use WP_Query() or get_posts(). From the WooCommerce doc:

wc_get_products and WC_Product_Query provide a standard way of retrieving products that is safe to use and will not break due to database changes in future WooCommerce versions. Building custom WP_Queries or database queries is likely to break your code in future versions of WooCommerce as data moves towards custom tables for better performance.

You can retrieve the products you want like this:

$args = array(
    'category' => array( 'hoodies' ),
    'orderby'  => 'name',
$products = wc_get_products( $args );

WooCommerce documentation

Note: the category argument takes an array of slugs, not IDs.

Generating unique random numbers (integers) between 0 and 'x'

I think, this is the most human approach (with using break from while loop), I explained it's mechanism in comments.

function generateRandomUniqueNumbersArray (limit) {

    //we need to store these numbers somewhere
    const array = new Array();
    //how many times we added a valid number (for if statement later)
    let counter = 0;

    //we will be generating random numbers until we are satisfied
    while (true) {

        //create that number
        const newRandomNumber = Math.floor(Math.random() * limit);

        //if we do not have this number in our array, we will add it
        if (!array.includes(newRandomNumber)) {

        //if we have enought of numbers, we do not need to generate them anymore
        if (counter >= limit) {

    //now hand over this stuff
    return array;

You can of course add different limit (your amount) to the last 'if' statement, if you need less numbers, but be sure, that it is less or equal to the limit of numbers itself - otherwise it will be infinite loop.