Programs & Examples On #Jackson

Jackson is a Java library for handling tasks like reading and writing (parsing / generating) and data binding to/from Java objects. Although primarily used for JSON, Jackson also supports many other data formats such as Avro, CBOR, CSV, Java Properties, Protobuf, Smile, XML and YAML.

how to create insert new nodes in JsonNode?

I've recently found even more interesting way to create any ValueNode or ContainerNode (Jackson v2.3).

ObjectNode node = JsonNodeFactory.instance.objectNode();

When is the @JsonProperty property used and what is it used for?

As you know, this is all about serialize and desalinize an object. Suppose there is an object:

public class Parameter {
  public String _name;
  public String _value; 
}

The serialization of this object is:

{
  "_name": "...",
  "_value": "..."
}

The name of variable is directly used to serialize data. If you are about to remove system api from system implementation, in some cases, you have to rename variable in serialization/deserialization. @JsonProperty is a meta data to tell serializer how to serial object. It is used to:

  • variable name
  • access (READ, WRITE)
  • default value
  • required/optional

from example:

public class Parameter {
  @JsonProperty(
        value="Name",
        required=true,
        defaultValue="No name",
        access= Access.READ_WRITE)
  public String _name;
  @JsonProperty(
        value="Value",
        required=true,
        defaultValue="Empty",
        access= Access.READ_WRITE)
  public String _value; 
}

Can not deserialize instance of java.util.ArrayList out of START_OBJECT token

I had this issue on a REST API that was created using Spring framework. Adding a @ResponseBody annotation (to make the response JSON) resolved it.

Jackson how to transform JsonNode to ArrayNode without casting?

In Java 8 you can do it like this:

import java.util.*;
import java.util.stream.*;

List<JsonNode> datasets = StreamSupport
    .stream(datasets.get("datasets").spliterator(), false)
    .collect(Collectors.toList())

Can not deserialize instance of java.util.ArrayList out of VALUE_STRING

For people that find this question by searching for the error message, you can also see this error if you make a mistake in your @JsonProperty annotations such that you annotate a List-typed property with the name of a single-valued field:

@JsonProperty("someSingleValuedField") // Oops, should have been "someMultiValuedField"
public List<String> getMyField() { // deserialization fails - single value into List
  return myField;
}

How to customise the Jackson JSON mapper implicitly used by Spring Boot?

A lot of things can configured in applicationproperties. Unfortunately this feature only in Version 1.3, but you can add in a Config-Class

@Autowired(required = true)
public void configureJackson(ObjectMapper jackson2ObjectMapper) {
    jackson2ObjectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
}

[UPDATE: You must work on the ObjectMapper because the build()-method is called before the config is runs.]

Parsing JSON in Spring MVC using Jackson JSON

I'm using json lib from http://json-lib.sourceforge.net/
json-lib-2.1-jdk15.jar

import net.sf.json.JSONObject;
...

public void send()
{
    //put attributes
    Map m = New HashMap();
    m.put("send_to","[email protected]");
    m.put("email_subject","this is a test email");
    m.put("email_content","test email content");

    //generate JSON Object
    JSONObject json = JSONObject.fromObject(content);
    String message = json.toString();
    ...
}

public void receive(String jsonMessage)
{
    //parse attributes
    JSONObject json = JSONObject.fromObject(jsonMessage);
    String to = (String) json.get("send_to");
    String title = (String) json.get("email_subject");
    String content = (String) json.get("email_content");
    ...
}

More samples here http://json-lib.sourceforge.net/usage.html

Jackson Vs. Gson

Gson 1.6 now includes a low-level streaming API and a new parser which is actually faster than Jackson.

Jackson JSON: get node name from json-tree

fields() and fieldNames() both were not working for me. And I had to spend quite sometime to find a way to iterate over the keys. There are two ways by which it can be done.

One is by converting it into a map (takes up more space):

ObjectMapper mapper = new ObjectMapper();
Map<String, Object> result = mapper.convertValue(jsonNode, Map.class);
for (String key : result.keySet())
{
    if(key.equals(foo))
    {
        //code here
    }
}

Another, by using a String iterator:

Iterator<String> it = jsonNode.getFieldNames();
while (it.hasNext())
{
    String key = it.next();
    if (key.equals(foo))
    {
         //code here
    }
}

Ignoring new fields on JSON objects using Jackson

I'm using jackson-xxx 2.8.5.Maven Dependency like:

<dependencies>
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>2.8.5</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.8.5</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.8.5</version>
    </dependency>

</dependencies>

First,If you want ignore unknown properties globally.you can config ObjectMapper.
Like below:

ObjectMapper objectMapper = new ObjectMapper();

objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

If you want ignore some class,you can add annotation @JsonIgnoreProperties(ignoreUnknown = true) on your class like:

@JsonIgnoreProperties(ignoreUnknown = true)
public class E1 {

    private String t1;

    public String getT1() {
        return t1;
    }

    public void setT1(String t1) {
        this.t1 = t1;
    }
}

Jackson overcoming underscores in favor of camel-case

If its a spring boot application, In application.properties file, just use

spring.jackson.property-naming-strategy=SNAKE_CASE

Or Annotate the model class with this annotation.

@JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy.class)

Date format Mapping to JSON Jackson

Of course there is an automated way called serialization and deserialization and you can define it with specific annotations (@JsonSerialize,@JsonDeserialize) as mentioned by pb2q as well.

You can use both java.util.Date and java.util.Calendar ... and probably JodaTime as well.

The @JsonFormat annotations not worked for me as I wanted (it has adjusted the timezone to different value) during deserialization (the serialization worked perfect):

@JsonFormat(locale = "hu", shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm", timezone = "CET")

@JsonFormat(locale = "hu", shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd HH:mm", timezone = "Europe/Budapest")

You need to use custom serializer and custom deserializer instead of the @JsonFormat annotation if you want predicted result. I have found real good tutorial and solution here http://www.baeldung.com/jackson-serialize-dates

There are examples for Date fields but I needed for Calendar fields so here is my implementation:

The serializer class:

public class CustomCalendarSerializer extends JsonSerializer<Calendar> {

    public static final SimpleDateFormat FORMATTER = new SimpleDateFormat("yyyy-MM-dd HH:mm");
    public static final Locale LOCALE_HUNGARIAN = new Locale("hu", "HU");
    public static final TimeZone LOCAL_TIME_ZONE = TimeZone.getTimeZone("Europe/Budapest");

    @Override
    public void serialize(Calendar value, JsonGenerator gen, SerializerProvider arg2)
            throws IOException, JsonProcessingException {
        if (value == null) {
            gen.writeNull();
        } else {
            gen.writeString(FORMATTER.format(value.getTime()));
        }
    }
}

The deserializer class:

public class CustomCalendarDeserializer extends JsonDeserializer<Calendar> {

    @Override
    public Calendar deserialize(JsonParser jsonparser, DeserializationContext context)
            throws IOException, JsonProcessingException {
        String dateAsString = jsonparser.getText();
        try {
            Date date = CustomCalendarSerializer.FORMATTER.parse(dateAsString);
            Calendar calendar = Calendar.getInstance(
                CustomCalendarSerializer.LOCAL_TIME_ZONE, 
                CustomCalendarSerializer.LOCALE_HUNGARIAN
            );
            calendar.setTime(date);
            return calendar;
        } catch (ParseException e) {
            throw new RuntimeException(e);
        }
    }
}

and the usage of the above classes:

public class CalendarEntry {

    @JsonSerialize(using = CustomCalendarSerializer.class)
    @JsonDeserialize(using = CustomCalendarDeserializer.class)
    private Calendar calendar;

    // ... additional things ...
}

Using this implementation the execution of the serialization and deserialization process consecutively results the origin value.

Only using the @JsonFormat annotation the deserialization gives different result I think because of the library internal timezone default setup what you can not change with annotation parameters (that was my experience with Jackson library 2.5.3 and 2.6.3 version as well).

Infinite Recursion with Jackson JSON and Hibernate JPA issue

The new annotation @JsonIgnoreProperties resolves many of the issues with the other options.

@Entity

public class Material{
   ...    
   @JsonIgnoreProperties("costMaterials")
   private List<Supplier> costSuppliers = new ArrayList<>();
   ...
}

@Entity
public class Supplier{
   ...
   @JsonIgnoreProperties("costSuppliers")
   private List<Material> costMaterials = new ArrayList<>();
   ....
}

Check it out here. It works just like in the documentation:
http://springquay.blogspot.com/2016/01/new-approach-to-solve-json-recursive.html

Should I declare Jackson's ObjectMapper as a static field?

Yes, that is safe and recommended.

The only caveat from the page you referred is that you can't be modifying configuration of the mapper once it is shared; but you are not changing configuration so that is fine. If you did need to change configuration, you would do that from the static block and it would be fine as well.

EDIT: (2013/10)

With 2.0 and above, above can be augmented by noting that there is an even better way: use ObjectWriter and ObjectReader objects, which can be constructed by ObjectMapper. They are fully immutable, thread-safe, meaning that it is not even theoretically possible to cause thread-safety issues (which can occur with ObjectMapper if code tries to re-configure instance).

Pretty printing JSON from Jackson 2.2's ObjectMapper

the IDENT_OUTPUT did not do anything for me, and to give a complete answer that works with my jackson 2.2.3 jars:

public static void main(String[] args) throws IOException {

byte[] jsonBytes = Files.readAllBytes(Paths.get("C:\\data\\testfiles\\single-line.json"));

ObjectMapper objectMapper = new ObjectMapper();

Object json = objectMapper.readValue( jsonBytes, Object.class );

System.out.println( objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString( json ) );
}

How to convert JSON string into List of Java object?

I made a method to do this below called jsonArrayToObjectList. Its a handy static class that will take a filename and the file contains an array in JSON form.

 List<Items> items = jsonArrayToObjectList(
            "domain/ItemsArray.json",  Item.class);

    public static <T> List<T> jsonArrayToObjectList(String jsonFileName, Class<T> tClass) throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        final File file = ResourceUtils.getFile("classpath:" + jsonFileName);
        CollectionType listType = mapper.getTypeFactory()
            .constructCollectionType(ArrayList.class, tClass);
        List<T> ts = mapper.readValue(file, listType);
        return ts;
    }

Strange Jackson exception being thrown when serializing Hibernate object

I had the same problem. See if you are using hibernatesession.load(). If so, try converting to hibernatesession.get(). This solved my problem.

Jackson: how to prevent field serialization

The easy way is to annotate your getters and setters.

Here is the original example modified to exclude the plain text password, but then annotate a new method that just returns the password field as encrypted text.

class User {

    private String password;

    public void setPassword(String password) {
        this.password = password;
    }

    @JsonIgnore
    public String getPassword() {
        return password;
    }

    @JsonProperty("password")
    public String getEncryptedPassword() {
        // encryption logic
    }
}

how to convert JSONArray to List of Object using camel-jackson

I also faced the similar problem with JSON output format. This code worked for me with the above JSON format.

package com.test.ameba;

import java.util.List;

public class OutputRanges {
    public List<Range> OutputRanges;
    public String Message;
    public String Entity;

    /**
     * @return the outputRanges
     */
    public List<Range> getOutputRanges() {
        return OutputRanges;
    }

    /**
     * @param outputRanges the outputRanges to set
     */
    public void setOutputRanges(List<Range> outputRanges) {
        OutputRanges = outputRanges;
    }

    /**
     * @return the message
     */
    public String getMessage() {
        return Message;
    }

    /**
     * @param message the message to set
     */
    public void setMessage(String message) {
        Message = message;
    }

    /**
     * @return the entity
     */
    public String getEntity() {
        return Entity;
    }

    /**
     * @param entity the entity to set
     */
    public void setEntity(String entity) {
        Entity = entity;
    }
}

package com.test;


public class Range {
    public String Name;
    /**
     * @return the name
     */
    public String getName() {
        return Name;
    }
    /**
     * @param name the name to set
     */
    public void setName(String name) {
        Name = name;
    }

    public Object[] Value;
    /**
     * @return the value
     */
    public Object[] getValue() {
        return Value;
    }
    /**
     * @param value the value to set
     */
    public void setValue(Object[] value) {
        Value = value;
    }

}

package com.test.ameba;

import java.io.IOException;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JSONTest {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String jsonString ="{\"OutputRanges\":[{\"Name\":\"ABF_MEDICAL_RELATIVITY\",\"Value\":[[1.3628407124839714]]},{\"Name\":\" ABF_RX_RELATIVITY\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_Unique_ID_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_FIRST_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_AMEBA_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_Effective_Date_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_AMEBA_MODEL\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_UC_ER_COPAY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_INN_OON_DED_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_COINSURANCE_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_PCP_SPEC_COPAY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_INN_OON_OOP_MAX_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_IP_OP_COPAY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_PHARMACY_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]},{\"Name\":\" ABF_PLAN_ADMIN_ERR\",\"Value\":[[\"CPD\",\"SL Limit\",\"Concat\",1,1.5,2,2.5,3]]}],\"Message\":\"\",\"Entity\":null}";
        ObjectMapper mapper = new ObjectMapper();
        OutputRanges OutputRanges=null;
        try {
            OutputRanges = mapper.readValue(jsonString, OutputRanges.class);
        } catch (JsonParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JsonMappingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("OutputRanges :: "+OutputRanges);;
        System.out.println("OutputRanges.getOutputRanges() :: "+OutputRanges.getOutputRanges());;
        for (Range r : OutputRanges.getOutputRanges()) {
            System.out.println(r.getName());
        }
    }

}

java.lang.ClassNotFoundException: com.fasterxml.jackson.annotation.JsonInclude$Value

I had different version of annotations jar. Changed all 3 jars to use SAME version of databind,annotations and core jackson jars

<dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>2.8.6</version>
</dependency>

Java 8 LocalDate Jackson format

In configuration class define LocalDateSerializer and LocalDateDeserializer class and register them to ObjectMapper via JavaTimeModule like below:

@Configuration
public class AppConfig
{
@Bean
    public ObjectMapper objectMapper()
    {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setSerializationInclusion(Include.NON_EMPTY);
        //other mapper configs
        // Customize de-serialization


        JavaTimeModule javaTimeModule = new JavaTimeModule();
        javaTimeModule.addSerializer(LocalDate.class, new LocalDateSerializer());
        javaTimeModule.addDeserializer(LocalDate.class, new LocalDateDeserializer());
        mapper.registerModule(javaTimeModule);

        return mapper;
    }

    public class LocalDateSerializer extends JsonSerializer<LocalDate> {
        @Override
        public void serialize(LocalDate value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
            gen.writeString(value.format(Constant.DATE_TIME_FORMATTER));
        }
    }

    public class LocalDateDeserializer extends JsonDeserializer<LocalDate> {

        @Override
        public LocalDate deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
            return LocalDate.parse(p.getValueAsString(), Constant.DATE_TIME_FORMATTER);
        }
    }
}

How to use Jackson to deserialise an array of objects

you could also create a class which extends ArrayList:

public static class MyList extends ArrayList<Myclass> {}

and then use it like:

List<MyClass> list = objectMapper.readValue(json, MyList.class);

Converting Java objects to JSON with Jackson

Note: To make the most voted solution work, attributes in the POJO have to be public or have a public getter/setter:

By default, Jackson 2 will only work with fields that are either public, or have a public getter method – serializing an entity that has all fields private or package private will fail.

Not tested yet, but I believe that this rule also applies for other JSON libs like google Gson.

How to convert the following json string to java object?

Gson gson = new Gson();
JsonParser parser = new JsonParser();
JsonObject object = (JsonObject) parser.parse(response);// response will be the json String
YourPojo emp = gson.fromJson(object, YourPojo.class); 

jackson deserialization json to java-objects

It looks like you are trying to read an object from JSON that actually describes an array. Java objects are mapped to JSON objects with curly braces {} but your JSON actually starts with square brackets [] designating an array.

What you actually have is a List<product> To describe generic types, due to Java's type erasure, you must use a TypeReference. Your deserialization could read: myProduct = objectMapper.readValue(productJson, new TypeReference<List<product>>() {});

A couple of other notes: your classes should always be PascalCased. Your main method can just be public static void main(String[] args) throws Exception which saves you all the useless catch blocks.

How to prevent null values inside a Map and null fields inside a bean from getting serialized through Jackson

If it's reasonable to alter the original Map data structure to be serialized to better represent the actual value wanted to be serialized, that's probably a decent approach, which would possibly reduce the amount of Jackson configuration necessary. For example, just remove the null key entries, if possible, before calling Jackson. That said...


To suppress serializing Map entries with null values:

Before Jackson 2.9

you can still make use of WRITE_NULL_MAP_VALUES, but note that it's moved to SerializationFeature:

mapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);

Since Jackson 2.9

The WRITE_NULL_MAP_VALUES is deprecated, you can use the below equivalent:

mapper.setDefaultPropertyInclusion(
   JsonInclude.Value.construct(Include.ALWAYS, Include.NON_NULL))

To suppress serializing properties with null values, you can configure the ObjectMapper directly, or make use of the @JsonInclude annotation:

mapper.setSerializationInclusion(Include.NON_NULL);

or:

@JsonInclude(Include.NON_NULL)
class Foo
{
  public String bar;

  Foo(String bar)
  {
    this.bar = bar;
  }
}

To handle null Map keys, some custom serialization is necessary, as best I understand.

A simple approach to serialize null keys as empty strings (including complete examples of the two previously mentioned configurations):

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.SerializerProvider;

public class JacksonFoo
{
  public static void main(String[] args) throws Exception
  {
    Map<String, Foo> foos = new HashMap<String, Foo>();
    foos.put("foo1", new Foo("foo1"));
    foos.put("foo2", new Foo(null));
    foos.put("foo3", null);
    foos.put(null, new Foo("foo4"));

    // System.out.println(new ObjectMapper().writeValueAsString(foos));
    // Exception: Null key for a Map not allowed in JSON (use a converting NullKeySerializer?)

    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(SerializationFeature.WRITE_NULL_MAP_VALUES, false);
    mapper.setSerializationInclusion(Include.NON_NULL);
    mapper.getSerializerProvider().setNullKeySerializer(new MyNullKeySerializer());
    System.out.println(mapper.writeValueAsString(foos));
    // output: 
    // {"":{"bar":"foo4"},"foo2":{},"foo1":{"bar":"foo1"}}
  }
}

class MyNullKeySerializer extends JsonSerializer<Object>
{
  @Override
  public void serialize(Object nullKey, JsonGenerator jsonGenerator, SerializerProvider unused) 
      throws IOException, JsonProcessingException
  {
    jsonGenerator.writeFieldName("");
  }
}

class Foo
{
  public String bar;

  Foo(String bar)
  {
    this.bar = bar;
  }
}

To suppress serializing Map entries with null keys, further custom serialization processing would be necessary.

Deserialize JSON with Jackson into Polymorphic Types - A Complete Example is giving me a compile error

Handling polymorphism is either model-bound or requires lots of code with various custom deserializers. I'm a co-author of a JSON Dynamic Deserialization Library that allows for model-independent json deserialization library. The solution to OP's problem can be found below. Note that the rules are declared in a very brief manner.

public class SOAnswer {
    @ToString @Getter @Setter
    @AllArgsConstructor @NoArgsConstructor
    public static abstract class Animal {
        private String name;    
    }

    @ToString(callSuper = true) @Getter @Setter
    @AllArgsConstructor @NoArgsConstructor
    public static class Dog extends Animal {
        private String breed;
    }

    @ToString(callSuper = true) @Getter @Setter
    @AllArgsConstructor @NoArgsConstructor
    public static class Cat extends Animal {
        private String favoriteToy;
    }
    
    
    public static void main(String[] args) {
        String json = "[{"
                + "    \"name\": \"pluto\","
                + "    \"breed\": \"dalmatian\""
                + "},{"
                + "    \"name\": \"whiskers\","
                + "    \"favoriteToy\": \"mouse\""
                + "}]";
        
        // create a deserializer instance
        DynamicObjectDeserializer deserializer = new DynamicObjectDeserializer();
        
        // runtime-configure deserialization rules; 
        // condition is bound to the existence of a field, but it could be any Predicate
        deserializer.addRule(DeserializationRuleFactory.newRule(1, 
                (e) -> e.getJsonNode().has("breed"),
                DeserializationActionFactory.objectToType(Dog.class)));
        
        deserializer.addRule(DeserializationRuleFactory.newRule(1, 
                (e) -> e.getJsonNode().has("favoriteToy"),
                DeserializationActionFactory.objectToType(Cat.class)));
        
        List<Animal> deserializedAnimals = deserializer.deserializeArray(json, Animal.class);
        
        for (Animal animal : deserializedAnimals) {
            System.out.println("Deserialized Animal Class: " + animal.getClass().getSimpleName()+";\t value: "+animal.toString());
        }
    }
}

Maven depenendency for pretius-jddl (check newest version at maven.org/jddl:

<dependency>
  <groupId>com.pretius</groupId>
  <artifactId>jddl</artifactId>
  <version>1.0.0</version>
</dependency>

Why when a constructor is annotated with @JsonCreator, its arguments must be annotated with @JsonProperty?

As precised in the annotation documentation, the annotation indicates that the argument name is used as the property name without any modifications, but it can be specified to non-empty value to specify different name:

Correct set of dependencies for using Jackson mapper

Apart from fixing the imports, do a fresh maven clean compile -U. Note the -U option, that brings in new dependencies which sometimes the editor has hard time with. Let the compilation fail due to un-imported classes, but at least you have an option to import them after the maven command.

Just doing Maven->Reimport from Intellij did not work for me.

Jackson enum Serializing and DeSerializer

I've found a very nice and concise solution, especially useful when you cannot modify enum classes as it was in my case. Then you should provide a custom ObjectMapper with a certain feature enabled. Those features are available since Jackson 1.6. So you only need to write toString() method in your enum.

public class CustomObjectMapper extends ObjectMapper {
    @PostConstruct
    public void customConfiguration() {
        // Uses Enum.toString() for serialization of an Enum
        this.enable(WRITE_ENUMS_USING_TO_STRING);
        // Uses Enum.toString() for deserialization of an Enum
        this.enable(READ_ENUMS_USING_TO_STRING);
    }
}

There are more enum-related features available, see here:

https://github.com/FasterXML/jackson-databind/wiki/Serialization-Features https://github.com/FasterXML/jackson-databind/wiki/Deserialization-Features

Convert Map to JSON using Jackson

You should prefer Object Mapper instead. Here is the link for the same : Object Mapper - Spring MVC way of Obect to JSON

Right way to write JSON deserializer in Spring or extend it

I was trying to @Autowire a Spring-managed service into my Deserializer. Somebody tipped me off to Jackson using the new operator when invoking the serializers/deserializers. This meant no auto-wiring of Jackson's instance of my Deserializer. Here's how I was able to @Autowire my service class into my Deserializer:

context.xml

<mvc:annotation-driven>
  <mvc:message-converters>
    <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
      <property name="objectMapper" ref="objectMapper" />
    </bean>
  </mvc:message-converters>
</mvc>
<bean id="objectMapper" class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
    <!-- Add deserializers that require autowiring -->
    <property name="deserializersByType">
        <map key-type="java.lang.Class">
            <entry key="com.acme.Anchor">
                <bean class="com.acme.AnchorDeserializer" />
            </entry>
        </map>
    </property>
</bean>

Now that my Deserializer is a Spring-managed bean, auto-wiring works!

AnchorDeserializer.java

public class AnchorDeserializer extends JsonDeserializer<Anchor> {
    @Autowired
    private AnchorService anchorService;
    public Anchor deserialize(JsonParser parser, DeserializationContext context)
             throws IOException, JsonProcessingException {
        // Do stuff
    }
}

AnchorService.java

@Service
public class AnchorService {}

Update: While my original answer worked for me back when I wrote this, @xi.lin's response is exactly what is needed. Nice find!

How to parse a JSON string into JsonNode in Jackson?

A slight variation on Richards answer but readTree can take a string so you can simplify it to:

ObjectMapper mapper = new ObjectMapper();
JsonNode actualObj = mapper.readTree("{\"k1\":\"v1\"}");

Convert JSON String to Pretty Print JSON output using Jackson

The simplest and also the most compact solution (for v2.3.3):

ObjectMapper mapper = new ObjectMapper();
mapper.enable(SerializationFeature.INDENT_OUTPUT);
mapper.writeValueAsString(obj)

How to modify JsonNode in Java?

The @Sharon-Ben-Asher answer is ok.

But in my case, for an array i have to use:

((ArrayNode) jsonNode).add("value");

Issue with parsing the content from json file with Jackson & message- JsonMappingException -Cannot deserialize as out of START_ARRAY token

JsonMappingException: out of START_ARRAY token exception is thrown by Jackson object mapper as it's expecting an Object {} whereas it found an Array [{}] in response.

This can be solved by replacing Object with Object[] in the argument for geForObject("url",Object[].class). References:

  1. Ref.1
  2. Ref.2
  3. Ref.3

Jackson and generic type reference

This is a well-known problem with Java type erasure: T is just a type variable, and you must indicate actual class, usually as Class argument. Without such information, best that can be done is to use bounds; and plain T is roughly same as 'T extends Object'. And Jackson will then bind JSON Objects as Maps.

In this case, tester method needs to have access to Class, and you can construct

JavaType type = mapper.getTypeFactory().
  constructCollectionType(List.class, Foo.class)

and then

List<Foo> list = mapper.readValue(new File("input.json"), type);

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.testing.models.Account

I have this method for deserializing an XML and converting the type:

public <T> Object deserialize(String xml, Class objClass ,TypeReference<T> typeReference ) throws IOException {
    XmlMapper xmlMapper = new XmlMapper();
    Object obj = xmlMapper.readValue(xml,objClass);
    return  xmlMapper.convertValue(obj,typeReference );   
}

and this is the call:

List<POJO> pojos = (List<POJO>) MyUtilClass.deserialize(xml, ArrayList.class,new TypeReference< List< POJO >>(){ });

How to specify jackson to only use fields - preferably globally

for jackson 1.9.10 I use

ObjectMapper mapper = new ObjectMapper();

mapper.setVisibility(JsonMethod.ALL, Visibility.NONE);
mapper.setVisibility(JsonMethod.FIELD, Visibility.ANY);

to turn of auto dedection.

How to tell Jackson to ignore a field during serialization if its value is null?

in my case

@JsonInclude(Include.NON_EMPTY)

made it work.

Only using @JsonIgnore during serialization, but not deserialization

Exactly how to do this depends on the version of Jackson that you're using. This changed around version 1.9, before that, you could do this by adding @JsonIgnore to the getter.

Which you've tried:

Add @JsonIgnore on the getter method only

Do this, and also add a specific @JsonProperty annotation for your JSON "password" field name to the setter method for the password on your object.

More recent versions of Jackson have added READ_ONLY and WRITE_ONLY annotation arguments for JsonProperty. So you could also do something like:

@JsonProperty(access = Access.WRITE_ONLY)
private String password;

Docs can be found here.

Casting LinkedHashMap to Complex Object

There is a good solution to this issue:

import com.fasterxml.jackson.databind.ObjectMapper;

ObjectMapper objectMapper = new ObjectMapper();

***DTO premierDriverInfoDTO = objectMapper.convertValue(jsonString, ***DTO.class); 

Map<String, String> map = objectMapper.convertValue(jsonString, Map.class);

Why did this issue occur? I guess you didn't specify the specific type when converting a string to the object, which is a class with a generic type, such as, User <T>.

Maybe there is another way to solve it, using Gson instead of ObjectMapper. (or see here Deserializing Generic Types with GSON)

Gson gson = new GsonBuilder().create();

Type type = new TypeToken<BaseResponseDTO<List<PaymentSummaryDTO>>>(){}.getType();

BaseResponseDTO<List<PaymentSummaryDTO>> results = gson.fromJson(jsonString, type);

BigDecimal revenue = results.getResult().get(0).getRevenue();

How to convert a JSON string to a Map<String, String> with Jackson JSON

ObjectReader reader = new ObjectMapper().readerFor(Map.class);

Map<String, String> map = reader.readValue("{\"foo\":\"val\"}");

Note that reader instance is Thread Safe.

Convert a Map<String, String> to a POJO

Yes, its definitely possible to avoid the intermediate conversion to JSON. Using a deep-copy tool like Dozer you can convert the map directly to a POJO. Here is a simplistic example:

Example POJO:

public class MyPojo implements Serializable {
    private static final long serialVersionUID = 1L;

    private String id;
    private String name;
    private Integer age;
    private Double savings;

    public MyPojo() {
        super();
    }

    // Getters/setters

    @Override
    public String toString() {
        return String.format(
                "MyPojo[id = %s, name = %s, age = %s, savings = %s]", getId(),
                getName(), getAge(), getSavings());
    }
}

Sample conversion code:

public class CopyTest {
    @Test
    public void testCopyMapToPOJO() throws Exception {
        final Map<String, String> map = new HashMap<String, String>(4);
        map.put("id", "5");
        map.put("name", "Bob");
        map.put("age", "23");
        map.put("savings", "2500.39");
        map.put("extra", "foo");

        final DozerBeanMapper mapper = new DozerBeanMapper();
        final MyPojo pojo = mapper.map(map, MyPojo.class);
        System.out.println(pojo);
    }
}

Output:

MyPojo[id = 5, name = Bob, age = 23, savings = 2500.39]

Note: If you change your source map to a Map<String, Object> then you can copy over arbitrarily deep nested properties (with Map<String, String> you only get one level).

Spring REST Service: how to configure to remove null objects in json response

I've found a solution through configuring the Spring container, but it's still not exactly what I wanted.

I rolled back to Spring 3.0.5, removed and in it's place I changed my config file to:

    <bean
    class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
        <list>
            <bean
                class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
                <property name="objectMapper" ref="jacksonObjectMapper" />
            </bean>
        </list>
    </property>
</bean>


<bean id="jacksonObjectMapper" class="org.codehaus.jackson.map.ObjectMapper" />
<bean id="jacksonSerializationConfig" class="org.codehaus.jackson.map.SerializationConfig"
    factory-bean="jacksonObjectMapper" factory-method="getSerializationConfig" />
<bean
    class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
    <property name="targetObject" ref="jacksonSerializationConfig" />
    <property name="targetMethod" value="setSerializationInclusion" />
    <property name="arguments">
        <list>
            <value type="org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion">NON_NULL</value>
        </list>
    </property>
</bean>

This is of course similar to responses given in other questions e.g.

configuring the jacksonObjectMapper not working in spring mvc 3

The important thing to note is that mvc:annotation-driven and AnnotationMethodHandlerAdapter cannot be used in the same context.

I'm still unable to get it working with Spring 3.1 and mvc:annotation-driven though. A solution that uses mvc:annotation-driven and all the benefits that accompany it would be far better I think. If anyone could show me how to do this, that would be great.

Jackson - Deserialize using generic class

You can't do that: you must specify fully resolved type, like Data<MyType>. T is just a variable, and as is meaningless.

But if you mean that T will be known, just not statically, you need to create equivalent of TypeReference dynamically. Other questions referenced may already mention this, but it should look something like:

public Data<T> read(InputStream json, Class<T> contentClass) {
   JavaType type = mapper.getTypeFactory().constructParametricType(Data.class, contentClass);
   return mapper.readValue(json, type);
}

Cannot construct instance of - Jackson

For me there was no default constructor defined for the POJOs I was trying to use. creating default constructor fixed it.

public class TeamCode {

    @Expose
    private String value;

    public String getValue() {
        return value;
    }

    **public TeamCode() {
    }**

    public TeamCode(String value) {
        this.value = value;
    }

    @Override
    public String toString() {
        return "TeamCode{" +
                "value='" + value + '\'' +
                '}';
    }

    public void setValue(String value) {
        this.value = value;
    }

}

Convert JsonNode into POJO

If you're using org.codehaus.jackson, this has been possible since 1.6. You can convert a JsonNode to a POJO with ObjectMapper#readValue: http://jackson.codehaus.org/1.9.4/javadoc/org/codehaus/jackson/map/ObjectMapper.html#readValue(org.codehaus.jackson.JsonNode, java.lang.Class)


    ObjectMapper mapper = new ObjectMapper();
    JsonParser jsonParser = mapper.getJsonFactory().createJsonParser("{\"foo\":\"bar\"}");
    JsonNode tree = jsonParser.readValueAsTree();
    // Do stuff to the tree
    mapper.readValue(tree, Foo.class);

Cannot deserialize instance of object out of START_ARRAY token in Spring Webservice

Your json contains an array, but you're trying to parse it as an object. This error occurs because objects must start with {.

You have 2 options:

  1. You can get rid of the ShopContainer class and use Shop[] instead

    ShopContainer response  = restTemplate.getForObject(
        url, ShopContainer.class);
    

    replace with

    Shop[] response  = restTemplate.getForObject(url, Shop[].class);
    

    and then make your desired object from it.

  2. You can change your server to return an object instead of a list

    return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(list);
    

    replace with

    return mapper.writerWithDefaultPrettyPrinter().writeValueAsString(
        new ShopContainer(list));
    

Jackson serialization: ignore empty values (or null)

You need to add import com.fasterxml.jackson.annotation.JsonInclude;

Add

@JsonInclude(JsonInclude.Include.NON_NULL)

on top of POJO

If you have nested POJO then

@JsonInclude(JsonInclude.Include.NON_NULL)

need to add on every values.

NOTE: JAXRS (Jersey) automatically handle this scenario 2.6 and above.

Serializing with Jackson (JSON) - getting "No serializer found"?

The problem in my case was Jackson was trying to serialize an empty object with no attributes nor methods.

As suggested in the exception I added the following line to avoid failure on empty beans:

For Jackson 1.9

myObjectMapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);

For Jackson 2.X

myObjectMapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);

You can find a simple example on jackson disable fail_on_empty_beans

Using Spring RestTemplate in generic method with generic parameter

I feel like there's a much easier way to do this... Just define a class with the type parameters that you want. e.g.:


final class MyClassWrappedByResponse extends ResponseWrapper<MyClass> {
    private static final long serialVersionUID = 1L;
}

Now change your code above to this and it should work:

public ResponseWrapper<MyClass> makeRequest(URI uri) {
    ResponseEntity<MyClassWrappedByResponse> response = template.exchange(
        uri,
        HttpMethod.POST,
        null,
        MyClassWrappedByResponse.class
    return response;
}

Convert Java Object to JsonNode in Jackson

As of Jackson 1.6, you can use:

JsonNode node = mapper.valueToTree(map);

or

JsonNode node = mapper.convertValue(object, JsonNode.class);

Source: is there a way to serialize pojo's directly to treemodel?

Jackson - How to process (deserialize) nested JSON?

I'm quite late to the party, but one approach is to use a static inner class to unwrap values:

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

class Scratch {
    private final String aString;
    private final String bString;
    private final String cString;
    private final static String jsonString;

    static {
        jsonString = "{\n" +
                "  \"wrap\" : {\n" +
                "    \"A\": \"foo\",\n" +
                "    \"B\": \"bar\",\n" +
                "    \"C\": \"baz\"\n" +
                "  }\n" +
                "}";
    }

    @JsonCreator
    Scratch(@JsonProperty("A") String aString,
            @JsonProperty("B") String bString,
            @JsonProperty("C") String cString) {
        this.aString = aString;
        this.bString = bString;
        this.cString = cString;
    }

    @Override
    public String toString() {
        return "Scratch{" +
                "aString='" + aString + '\'' +
                ", bString='" + bString + '\'' +
                ", cString='" + cString + '\'' +
                '}';
    }

    public static class JsonDeserializer {
        private final Scratch scratch;

        @JsonCreator
        public JsonDeserializer(@JsonProperty("wrap") Scratch scratch) {
            this.scratch = scratch;
        }

        public Scratch getScratch() {
            return scratch;
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper objectMapper = new ObjectMapper();
        Scratch scratch = objectMapper.readValue(jsonString, Scratch.JsonDeserializer.class).getScratch();
        System.out.println(scratch.toString());
    }
}

However, it's probably easier to use objectMapper.configure(SerializationConfig.Feature.UNWRAP_ROOT_VALUE, true); in conjunction with @JsonRootName("aName"), as pointed out by pb2q

Spring configure @ResponseBody JSON format

I wrote my own FactoryBean which instantiates an ObjectMapper (simplified version):

 public class ObjectMapperFactoryBean implements FactoryBean<ObjectMapper>{

        @Override
        public ObjectMapper getObject() throws Exception {
                ObjectMapper mapper = new ObjectMapper();
                mapper.getSerializationConfig().setSerializationInclusion(JsonSerialize.Inclusion.NON_NULL);
                return mapper;
        }

        @Override
        public Class<?> getObjectType() {
                return ObjectMapper.class;
        }

        @Override
        public boolean isSingleton() {
                return true;
        }

}

And the usage in the spring configuration:

<bean
    class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
        <list>
            <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
                <property name="objectMapper" ref="jacksonObjectMapper" />
            </bean>
        </list>
    </property>
</bean>

Jackson with JSON: Unrecognized field, not marked as ignorable

The shortest solution without setter/getter is to add @JsonProperty to a class field:

public class Wrapper {
    @JsonProperty
    private List<Student> wrapper;
}

public class Student {
    @JsonProperty
    private String name;
    @JsonProperty
    private String id;
}

Also, you called students list "wrapper" in your json, so Jackson expects a class with a field called "wrapper".

How can I tell jackson to ignore a property for which I don't have control over the source code?

One other possibility is, if you want to ignore all unknown properties, you can configure the mapper as follows:

mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

JsonMappingException: No suitable constructor found for type [simple type, class ]: can not instantiate from JSON object

Failing custom jackson Serializers/Deserializers could also be the problem. Though it's not your case, it's worth mentioning.

I faced the same exception and that was the case.

Spring Rest POST Json RequestBody Content type not supported

I had the same issue. Root cause was using custom deserializer without default constructor.

How do I use a custom Serializer with Jackson?

I wrote an example for a custom Timestamp.class serialization/deserialization, but you could use it for what ever you want.

When creating the object mapper do something like this:

public class JsonUtils {

    public static ObjectMapper objectMapper = null;

    static {
        objectMapper = new ObjectMapper();
        SimpleModule s = new SimpleModule();
        s.addSerializer(Timestamp.class, new TimestampSerializerTypeHandler());
        s.addDeserializer(Timestamp.class, new TimestampDeserializerTypeHandler());
        objectMapper.registerModule(s);
    };
}

for example in java ee you could initialize it with this:

import java.time.LocalDateTime;

import javax.ws.rs.ext.ContextResolver;
import javax.ws.rs.ext.Provider;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;

@Provider
public class JacksonConfig implements ContextResolver<ObjectMapper> {

    private final ObjectMapper objectMapper;

    public JacksonConfig() {
        objectMapper = new ObjectMapper();
        SimpleModule s = new SimpleModule();
        s.addSerializer(Timestamp.class, new TimestampSerializerTypeHandler());
        s.addDeserializer(Timestamp.class, new TimestampDeserializerTypeHandler());
        objectMapper.registerModule(s);
    };

    @Override
    public ObjectMapper getContext(Class<?> type) {
        return objectMapper;
    }
}

where the serializer should be something like this:

import java.io.IOException;
import java.sql.Timestamp;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;

public class TimestampSerializerTypeHandler extends JsonSerializer<Timestamp> {

    @Override
    public void serialize(Timestamp value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        String stringValue = value.toString();
        if(stringValue != null && !stringValue.isEmpty() && !stringValue.equals("null")) {
            jgen.writeString(stringValue);
        } else {
            jgen.writeNull();
        }
    }

    @Override
    public Class<Timestamp> handledType() {
        return Timestamp.class;
    }
}

and deserializer something like this:

import java.io.IOException;
import java.sql.Timestamp;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.SerializerProvider;

public class TimestampDeserializerTypeHandler extends JsonDeserializer<Timestamp> {

    @Override
    public Timestamp deserialize(JsonParser jp, DeserializationContext ds) throws IOException, JsonProcessingException {
        SqlTimestampConverter s = new SqlTimestampConverter();
        String value = jp.getValueAsString();
        if(value != null && !value.isEmpty() && !value.equals("null"))
            return (Timestamp) s.convert(Timestamp.class, value);
        return null;
    }

    @Override
    public Class<Timestamp> handledType() {
        return Timestamp.class;
    }
}

Different names of JSON property during serialization and deserialization

You can use a combination of @JsonSetter, and @JsonGetter to control the deserialization, and serialization of your property, respectively. This will also allow you to keep standardized getter and setter method names that correspond to your actual field name.

import com.fasterxml.jackson.annotation.JsonSetter;    
import com.fasterxml.jackson.annotation.JsonGetter;

class Coordinates {
    private int red;

    //# Used during serialization
    @JsonGetter("r")
    public int getRed() {
        return red;
    }

    //# Used during deserialization
    @JsonSetter("red")
    public void setRed(int red) {
        this.red = red;
    }
}

How to deserialize JS date using Jackson?

In addition to Varun Achar's answer, this is the Java 8 variant I came up with, that uses java.time.LocalDate and ZonedDateTime instead of the old java.util.Date classes.

public class LocalDateDeserializer extends JsonDeserializer<LocalDate> {

    @Override
    public LocalDate deserialize(JsonParser jsonparser, DeserializationContext deserializationcontext) throws IOException {

        String string = jsonparser.getText();

        if(string.length() > 20) {
            ZonedDateTime zonedDateTime = ZonedDateTime.parse(string);
            return zonedDateTime.toLocalDate();
        }

        return LocalDate.parse(string);
    }
  }

Required request body content is missing: org.springframework.web.method.HandlerMethod$HandlerMethodParameter

Sorry guys.. actually because of a csrf token was needed I was getting that issue. I have implemented spring security and csrf is enable. And through ajax call I need to pass the csrf token.

Set Jackson Timezone for Date deserialization

Have you tried this in your application.properties?

spring.jackson.time-zone= # Time zone used when formatting dates. For instance `America/Los_Angeles`

JSON Invalid UTF-8 middle byte

JSON data must be encoded as UTF-8, UTF-16 or UTF-32. The JSON decoder can determine the encoding by examining the first four octets of the byte stream:

       00 00 00 xx  UTF-32BE
       00 xx 00 xx  UTF-16BE
       xx 00 00 00  UTF-32LE
       xx 00 xx 00  UTF-16LE
       xx xx xx xx  UTF-8

It sounds like the server is encoding data in some illegal encoding (ISO-8859-1, windows-1252, etc.)

Parsing JSON in Java without knowing JSON format

Find the following code for Unknown Json Object parsing using Gson library.

public class JsonParsing {
static JsonParser parser = new JsonParser();

public static HashMap<String, Object> createHashMapFromJsonString(String json) {

    JsonObject object = (JsonObject) parser.parse(json);
    Set<Map.Entry<String, JsonElement>> set = object.entrySet();
    Iterator<Map.Entry<String, JsonElement>> iterator = set.iterator();
    HashMap<String, Object> map = new HashMap<String, Object>();

    while (iterator.hasNext()) {

        Map.Entry<String, JsonElement> entry = iterator.next();
        String key = entry.getKey();
        JsonElement value = entry.getValue();

        if (null != value) {
            if (!value.isJsonPrimitive()) {
                if (value.isJsonObject()) {

                    map.put(key, createHashMapFromJsonString(value.toString()));
                } else if (value.isJsonArray() && value.toString().contains(":")) {

                    List<HashMap<String, Object>> list = new ArrayList<>();
                    JsonArray array = value.getAsJsonArray();
                    if (null != array) {
                        for (JsonElement element : array) {
                            list.add(createHashMapFromJsonString(element.toString()));
                        }
                        map.put(key, list);
                    }
                } else if (value.isJsonArray() && !value.toString().contains(":")) {
                    map.put(key, value.getAsJsonArray());
                }
            } else {
                map.put(key, value.getAsString());
            }
        }
    }
    return map;
}
}

Jackson - best way writes a java list to a json array

In objectMapper we have writeValueAsString() which accepts object as parameter. We can pass object list as parameter get the string back.

List<Apartment> aptList =  new ArrayList<Apartment>();
    Apartment aptmt = null;
    for(int i=0;i<5;i++){
         aptmt= new Apartment();
         aptmt.setAptName("Apartment Name : ArrowHead Ranch");
         aptmt.setAptNum("3153"+i);
         aptmt.setPhase((i+1));
         aptmt.setFloorLevel(i+2);
         aptList.add(aptmt);
    }
mapper.writeValueAsString(aptList)

JsonParseException: Unrecognized token 'http': was expecting ('true', 'false' or 'null')

It might be obvious, but make sure that you are sending to the parser URL object not a String containing www adress. This will not work:

    ObjectMapper mapper = new ObjectMapper();
    String www = "www.sample.pl";
    Weather weather = mapper.readValue(www, Weather.class);

But this will:

    ObjectMapper mapper = new ObjectMapper();
    URL www = new URL("http://www.oracle.com/");
    Weather weather = mapper.readValue(www, Weather.class);

How do I disable fail_on_empty_beans in Jackson?

You can also get the same issue if your class doesn't contain any public methods/properties. I normally have dedicated DTOs for API requests and responses, declared public, but forgot in one case to make the methods public as well - which caused the "empty" bean in the first place.

Representing null in JSON

I would use null to show that there is no value for that particular key. For example, use null to represent that "number of devices in your household connects to internet" is unknown.

On the other hand, use {} if that particular key is not applicable. For example, you should not show a count, even if null, to the question "number of cars that has active internet connection" is asked to someone who does not own any cars.

I would avoid defaulting any value unless that default makes sense. While you may decide to use null to represent no value, certainly never use "null" to do so.

Setting default values to null fields when mapping with Jackson

There is no annotation to set default value.
You can set default value only on java class level:

public class JavaObject 
{
    public String notNullMember;

    public String optionalMember = "Value";
}

Can not deserialize instance of java.lang.String out of START_ARRAY token

The error is:

Can not deserialize instance of java.lang.String out of START_ARRAY token at [Source: line: 1, column: 1095] (through reference chain: JsonGen["platforms"])

In JSON, platforms look like this:

"platforms": [
    {
        "platform": "iphone"
    },
    {
        "platform": "ipad"
    },
    {
        "platform": "android_phone"
    },
    {
        "platform": "android_tablet"
    }
]

So try change your pojo to something like this:

private List platforms;

public List getPlatforms(){
    return this.platforms;
}

public void setPlatforms(List platforms){
    this.platforms = platforms;
}

EDIT: you will need change mobile_networks too. Will look like this:

private List mobile_networks;

public List getMobile_networks() {
    return mobile_networks;
}

public void setMobile_networks(List mobile_networks) {
    this.mobile_networks = mobile_networks;
}

Deserialize JSON to ArrayList<POJO> using Jackson

I am also having the same problem. I have a json which is to be converted to ArrayList.

Account looks like this.

Account{
  Person p ;
  Related r ;

}

Person{
    String Name ;
    Address a ;
}

All of the above classes have been annotated properly. I have tried TypeReference>() {} but is not working.

It gives me Arraylist but ArrayList has a linkedHashMap which contains some more linked hashmaps containing final values.

My code is as Follows:

public T unmarshal(String responseXML,String c)
{
    ObjectMapper mapper = new ObjectMapper();

    AnnotationIntrospector introspector = new JacksonAnnotationIntrospector();

    mapper.getDeserializationConfig().withAnnotationIntrospector(introspector);

    mapper.getSerializationConfig().withAnnotationIntrospector(introspector);
    try
    {
      this.targetclass = (T) mapper.readValue(responseXML,  new TypeReference<ArrayList<T>>() {});
    }
    catch (JsonParseException e)
    {
      e.printStackTrace();
    }
    catch (JsonMappingException e) {
      e.printStackTrace();
    } catch (IOException e) {
      e.printStackTrace();
    }

    return this.targetclass;
}

I finally solved the problem. I am able to convert the List in Json String directly to ArrayList as follows:

JsonMarshallerUnmarshaller<T>{

     T targetClass ;

     public ArrayList<T> unmarshal(String jsonString)
     {
        ObjectMapper mapper = new ObjectMapper();

        AnnotationIntrospector introspector = new JacksonAnnotationIntrospector();

        mapper.getDeserializationConfig().withAnnotationIntrospector(introspector);

        mapper.getSerializationConfig().withAnnotationIntrospector(introspector);
        JavaType type = mapper.getTypeFactory().
                    constructCollectionType(ArrayList.class, targetclass.getClass()) ;
        try
        {
        Class c1 = this.targetclass.getClass() ;
        Class c2 = this.targetclass1.getClass() ;
            ArrayList<T> temp = (ArrayList<T>) mapper.readValue(jsonString,  type);
        return temp ;
        }
       catch (JsonParseException e)
       {
        e.printStackTrace();
       }
       catch (JsonMappingException e) {
           e.printStackTrace();
       } catch (IOException e) {
          e.printStackTrace();
       }

     return null ;
    }  

}

How to serialize Joda DateTime with Jackson JSON processor?

The easy solution

I have encountered similar problem and my solution is much clear than above.

I simply used the pattern in @JsonFormat annotation

Basically my class has a DateTime field, so I put an annotation around the getter:

@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
public DateTime getDate() {
    return date;
}

I serialize the class with ObjectMapper

    ObjectMapper mapper = new ObjectMapper();
    mapper.registerModule(new JodaModule());
    mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
    ObjectWriter ow = mapper.writer();
    try {
        String logStr = ow.writeValueAsString(log);
        outLogger.info(logStr);
    } catch (IOException e) {
        logger.warn("JSON mapping exception", e);
    }

We use Jackson 2.5.4

Jackson JSON custom serialization for certain fields

Add a @JsonProperty annotated getter, which returns a String, for the favoriteNumber field:

public class Person {
    public String name;
    public int age;
    private int favoriteNumber;

    public Person(String name, int age, int favoriteNumber) {
        this.name = name;
        this.age = age;
        this.favoriteNumber = favoriteNumber;
    }

    @JsonProperty
    public String getFavoriteNumber() {
        return String.valueOf(favoriteNumber);
    }

    public static void main(String... args) throws Exception {
        Person p = new Person("Joe", 25, 123);
        ObjectMapper mapper = new ObjectMapper();
        System.out.println(mapper.writeValueAsString(p)); 
        // {"name":"Joe","age":25,"favoriteNumber":"123"}
    }
}

Java to Jackson JSON serialization: Money fields

Inspired by Steve, and as the updates for Java 11. Here's how we did the BigDecimal reformatting to avoid scientific notation.

public class PriceSerializer extends JsonSerializer<BigDecimal> {
    @Override
    public void serialize(BigDecimal value, JsonGenerator jgen, SerializerProvider provider) throws IOException {
        // Using writNumber and removing toString make sure the output is number but not String.
        jgen.writeNumber(value.setScale(2, RoundingMode.HALF_UP));
    }
}

receiving json and deserializing as List of object at spring mvc controller

I believe this will solve the issue

var z = '[{"name":"1","age":"2"},{"name":"1","age":"3"}]';
z = JSON.stringify(JSON.parse(z));
$.ajax({
    url: "/setTest",
    data: z,
    type: "POST",
    dataType:"json",
    contentType:'application/json'               
});

How to parse a JSON string to an array using Jackson

I finally got it:

ObjectMapper objectMapper = new ObjectMapper();
TypeFactory typeFactory = objectMapper.getTypeFactory();
List<SomeClass> someClassList = objectMapper.readValue(jsonString, typeFactory.constructCollectionType(List.class, SomeClass.class));

Converting JSON data to Java object

I looked at Google's Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

Google Gson supports generics and nested beans. The [] in JSON represents an array and should map to a Java collection such as List or just a plain Java array. The {} in JSON represents an object and should map to a Java Map or just some JavaBean class.

You have a JSON object with several properties of which the groups property represents an array of nested objects of the very same type. This can be parsed with Gson the following way:

package com.stackoverflow.q1688099;

import java.util.List;
import com.google.gson.Gson;

public class Test {

    public static void main(String... args) throws Exception {
        String json = 
            "{"
                + "'title': 'Computing and Information systems',"
                + "'id' : 1,"
                + "'children' : 'true',"
                + "'groups' : [{"
                    + "'title' : 'Level one CIS',"
                    + "'id' : 2,"
                    + "'children' : 'true',"
                    + "'groups' : [{"
                        + "'title' : 'Intro To Computing and Internet',"
                        + "'id' : 3,"
                        + "'children': 'false',"
                        + "'groups':[]"
                    + "}]" 
                + "}]"
            + "}";

        // Now do the magic.
        Data data = new Gson().fromJson(json, Data.class);

        // Show it.
        System.out.println(data);
    }

}

class Data {
    private String title;
    private Long id;
    private Boolean children;
    private List<Data> groups;

    public String getTitle() { return title; }
    public Long getId() { return id; }
    public Boolean getChildren() { return children; }
    public List<Data> getGroups() { return groups; }

    public void setTitle(String title) { this.title = title; }
    public void setId(Long id) { this.id = id; }
    public void setChildren(Boolean children) { this.children = children; }
    public void setGroups(List<Data> groups) { this.groups = groups; }
    
    public String toString() {
        return String.format("title:%s,id:%d,children:%s,groups:%s", title, id, children, groups);
    }
}

Fairly simple, isn't it? Just have a suitable JavaBean and call Gson#fromJson().

See also:

@JsonProperty annotation on field as well as getter/setter

My observations based on a few tests has been that whichever name differs from the property name is one which takes effect:

For eg. consider a slight modification of your case:

@JsonProperty("fileName")
private String fileName;

@JsonProperty("fileName")
public String getFileName()
{
    return fileName;
}

@JsonProperty("fileName1")
public void setFileName(String fileName)
{
    this.fileName = fileName;
}

Both fileName field, and method getFileName, have the correct property name of fileName and setFileName has a different one fileName1, in this case Jackson will look for a fileName1 attribute in json at the point of deserialization and will create a attribute called fileName1 at the point of serialization.

Now, coming to your case, where all the three @JsonProperty differ from the default propertyname of fileName, it would just pick one of them as the attribute(FILENAME), and had any on of the three differed, it would have thrown an exception:

java.lang.IllegalStateException: Conflicting property name definitions

No Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator

Just want to point out that this answer provides a better explanation.
Basically you can either have @Getter and @NoArgConstructor together
or let Lombok regenerates @ConstructorProperties using lombok.config file,
or compile your java project with -parameters flags,
or let Jackson use Lombok's @Builder

How to change a field name in JSON using Jackson

There is one more option to rename field:

Jackson MixIns.

Useful if you deal with third party classes, which you are not able to annotate, or you just do not want to pollute the class with Jackson specific annotations.

The Jackson documentation for Mixins is outdated, so this example can provide more clarity. In essence: you create mixin class which does the serialization in the way you want. Then register it to the ObjectMapper:

objectMapper.addMixIn(ThirdParty.class, MyMixIn.class);

Configuring ObjectMapper in Spring

If you want to add custom ObjectMapper for registering custom serializers, try my answer.

In my case (Spring 3.2.4 and Jackson 2.3.1), XML configuration for custom serializer:

<mvc:annotation-driven>
    <mvc:message-converters register-defaults="false">
        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                    <property name="serializers">
                        <array>
                            <bean class="com.example.business.serializer.json.CustomObjectSerializer"/>
                        </array>
                    </property>
                </bean>
            </property>
        </bean>
    </mvc:message-converters>
</mvc:annotation-driven>

was in unexplained way overwritten back to default by something.

This worked for me:

CustomObject.java

@JsonSerialize(using = CustomObjectSerializer.class)
public class CustomObject {

    private Long value;

    public Long getValue() {
        return value;
    }

    public void setValue(Long value) {
        this.value = value;
    }
}

CustomObjectSerializer.java

public class CustomObjectSerializer extends JsonSerializer<CustomObject> {

    @Override
    public void serialize(CustomObject value, JsonGenerator jgen,
        SerializerProvider provider) throws IOException,JsonProcessingException {
        jgen.writeStartObject();
        jgen.writeNumberField("y", value.getValue());
        jgen.writeEndObject();
    }

    @Override
    public Class<CustomObject> handledType() {
        return CustomObject.class;
    }
}

No XML configuration (<mvc:message-converters>(...)</mvc:message-converters>) is needed in my solution.

Deserialize Java 8 LocalDateTime with JacksonMapper

You can implement your JsonSerializer

See:

That your propertie in bean

@JsonProperty("start_date")
@JsonFormat("YYYY-MM-dd HH:mm")
@JsonSerialize(using = DateSerializer.class)
private Date startDate;

That way implement your custom class

public class DateSerializer extends JsonSerializer<Date> implements ContextualSerializer<Date> {

    private final String format;

    private DateSerializer(final String format) {
        this.format = format;
    }

    public DateSerializer() {
        this.format = null;
    }

    @Override
    public void serialize(final Date value, final JsonGenerator jgen, final SerializerProvider provider) throws IOException {
        jgen.writeString(new SimpleDateFormat(format).format(value));
    }

    @Override
    public JsonSerializer<Date> createContextual(final SerializationConfig serializationConfig, final BeanProperty beanProperty) throws JsonMappingException {
        final AnnotatedElement annotated = beanProperty.getMember().getAnnotated();
        return new DateSerializer(annotated.getAnnotation(JsonFormat.class).value());
    }

}

Try this after post result for us.

serialize/deserialize java 8 java.time with Jackson JSON mapper

This is just an example how to use it in a unit test that I hacked to debug this issue. The key ingredients are

  • mapper.registerModule(new JavaTimeModule());
  • maven dependency of <artifactId>jackson-datatype-jsr310</artifactId>

Code:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import org.testng.Assert;
import org.testng.annotations.Test;

import java.io.IOException;
import java.io.Serializable;
import java.time.Instant;

class Mumu implements Serializable {
    private Instant from;
    private String text;

    Mumu(Instant from, String text) {
        this.from = from;
        this.text = text;
    }

    public Mumu() {
    }

    public Instant getFrom() {
        return from;
    }

    public String getText() {
        return text;
    }

    @Override
    public String toString() {
        return "Mumu{" +
                "from=" + from +
                ", text='" + text + '\'' +
                '}';
    }
}
public class Scratch {


    @Test
    public void JacksonInstant() throws IOException {
        ObjectMapper mapper = new ObjectMapper();
        mapper.registerModule(new JavaTimeModule());

        Mumu before = new Mumu(Instant.now(), "before");
        String jsonInString = mapper.writeValueAsString(before);


        System.out.println("-- BEFORE --");
        System.out.println(before);
        System.out.println(jsonInString);

        Mumu after = mapper.readValue(jsonInString, Mumu.class);
        System.out.println("-- AFTER --");
        System.out.println(after);

        Assert.assertEquals(after.toString(), before.toString());
    }

}

No content to map due to end-of-input jackson parser

A simple fix could be Content-Type: application/json

You are probably making a REST API call to get the response.

Mostly you are not setting Content-Type: application/json when you the request. Content-Type: application/x-www-form-urlencoded will be chosen which might be causing this exception.

Serializing enums with Jackson

Here is my solution. I want transform enum to {id: ..., name: ...} form.

With Jackson 1.x:

pom.xml:

<properties>
    <jackson.version>1.9.13</jackson.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-core-asl</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.jackson</groupId>
        <artifactId>jackson-mapper-asl</artifactId>
        <version>${jackson.version}</version>
    </dependency>
</dependencies>

Rule.java:

import org.codehaus.jackson.map.annotate.JsonSerialize;
import my.NamedEnumJsonSerializer;
import my.NamedEnum;

@Entity
@Table(name = "RULE")
public class Rule {
    @Column(name = "STATUS", nullable = false, updatable = true)
    @Enumerated(EnumType.STRING)
    @JsonSerialize(using = NamedEnumJsonSerializer.class)
    private Status status;
    public Status getStatus() { return status; }
    public void setStatus(Status status) { this.status = status; }

    public static enum Status implements NamedEnum {
        OPEN("open rule"),
        CLOSED("closed rule"),
        WORKING("rule in work");

        private String name;
        Status(String name) { this.name = name; }
        public String getName() { return this.name; }
    };
}

NamedEnum.java:

package my;

public interface NamedEnum {
    String name();
    String getName();
}

NamedEnumJsonSerializer.java:

package my;

import my.NamedEnum;
import java.io.IOException;
import java.util.*;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.JsonSerializer;
import org.codehaus.jackson.map.SerializerProvider;

public class NamedEnumJsonSerializer extends JsonSerializer<NamedEnum> {
    @Override
    public void serialize(NamedEnum value, JsonGenerator jgen, SerializerProvider provider) throws IOException, JsonProcessingException {
        Map<String, String> map = new HashMap<>();
        map.put("id", value.name());
        map.put("name", value.getName());
        jgen.writeObject(map);
    }
}

With Jackson 2.x:

pom.xml:

<properties>
    <jackson.version>2.3.3</jackson.version>
</properties>

<dependencies>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson.version}</version>
    </dependency>
</dependencies>

Rule.java:

import com.fasterxml.jackson.annotation.JsonFormat;

@Entity
@Table(name = "RULE")
public class Rule {
    @Column(name = "STATUS", nullable = false, updatable = true)
    @Enumerated(EnumType.STRING)
    private Status status;
    public Status getStatus() { return status; }
    public void setStatus(Status status) { this.status = status; }

    @JsonFormat(shape = JsonFormat.Shape.OBJECT)
    public static enum Status {
        OPEN("open rule"),
        CLOSED("closed rule"),
        WORKING("rule in work");

        private String name;
        Status(String name) { this.name = name; }
        public String getName() { return this.name; }
        public String getId() { return this.name(); }
    };
}

Rule.Status.CLOSED translated to {id: "CLOSED", name: "closed rule"}.

JSON parse error: Can not construct instance of java.time.LocalDate: no String-argument constructor/factory method to deserialize from String value

Spring Boot 2.2.2 / Gradle:

Gradle (build.gradle):

implementation("com.fasterxml.jackson.datatype:jackson-datatype-jsr310")

Entity (User.class):

LocalDate dateOfBirth;

Code:

ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());
User user = mapper.readValue(json, User.class);

Browse files and subfolders in Python

Slightly altered version of Sven Marnach's solution..


import os

folder_location = 'C:\SomeFolderName' file_list = create_file_list(folder_location)

def create_file_list(path): return_list = []

for filenames in os.walk(path): for file_list in filenames: for file_name in file_list: if file_name.endswith((".txt")): return_list.append(file_name) return return_list

Questions every good PHP Developer should be able to answer

Admittedly, I stole this question from somewhere else (can't remember where I read it any more) but thought it was funny:

Q: What is T_PAAMAYIM_NEKUDOTAYIM?
A: Its the scope resolution operator (double colon)

An experienced PHP'er immediately knows what it means. Less experienced (and not Hebrew) developers may want to read this.

But more serious questions now:


Q: What is the cause of this warning: 'Warning: Cannot modify header information - headers already sent', and what is a good practice to prevent it?
A: Cause: body data was sent, causing headers to be sent too.
Prevention: Be sure to execute header specific code first before you output any body data. Be sure you haven't accidentally sent out whitespace or any other characters.


Q: What is wrong with this query: "SELECT * FROM table WHERE id = $_POST[ 'id' ]"?
A: 1. It is vulnarable to SQL injection. Never use user input directly in queries. Sanitize it first. Preferebly use prepared statements (PDO) 2. Don't select all columns (*), but specify every single column. This is predominantly ment to prevent queries hogging up memory when for instance a BLOB column is added at some point in the future.


Q: What is wrong with this if statement: if( !strpos( $haystack, $needle ) ...?
A: strpos returns the index position of where it first found the $needle, which could be 0. Since 0 also resolves to false the solution is to use strict comparison: if( false !== strpos( $haystack, $needle )...


Q: What is the preferred way to write this if statement, and why?
if( 5 == $someVar ) or if( $someVar == 5 )
A: The former, as it prevents accidental assignment of 5 to $someVar when you forget to use 2 equalsigns ($someVar = 5), and will cause an error, the latter won't.


Q: Given this code:

function doSomething( &$arg )
{
    $return = $arg;
    $arg += 1;
    return $return;
}

$a = 3;
$b = doSomething( $a );

...what is the value of $a and $b after the function call and why?
A: $a is 4 and $b is 3. The former because $arg is passed by reference, the latter because the return value of the function is a copy of (not a reference to) the initial value of the argument.


OOP specific

Q: What is the difference between public, protected and private in a class definition?
A: public makes a class member available to "everyone", protected makes the class member available to only itself and derived classes, private makes the class member only available to the class itself.


Q: What is wrong with this code:

class SomeClass
{
    protected $_someMember;

    public function __construct()
    {
        $this->_someMember = 1;
    }

    public static function getSomethingStatic()
    {
        return $this->_someMember * 5; // here's the catch
    }
}

A: Static methods don't have access to $this, because static methods can be executed without instantiating a class.


Q: What is the difference between an interface and an abstract class?
A: An interface defines a contract between an implementing class is and an object that calls the interface. An abstract class pre-defines certain behaviour for classes that will extend it. To a certain degree this can also be considered a contract, since it garantuees certain methods to exist.


Q: What is wrong with classes that predominantly define getters and setters, that map straight to it's internal members, without actually having methods that execute behaviour?
A: This might be a code smell since the object acts as an ennobled array, without much other use.


Q: Why is PHP's implementation of the use of interfaces sub-optimal?
A: PHP doesn't allow you to define the expected return type of the method's, which essentially renders interfaces pretty useless. :-P

c++ compile error: ISO C++ forbids comparison between pointer and integer

You have two ways to fix this. The preferred way is to use:

string answer;

(instead of char). The other possible way to fix it is:

if (answer == 'y') ...

(note single quotes instead of double, representing a char constant).

Node.js Hostname/IP doesn't match certificate's altnames

If you are going to trust a sub-domain, for example, aaa.localhost, Please don't do it like mkcert localhost *.localhost 127.0.0.1, this will not work since some browser doesn't accept wildcard subdomain.

Maybe try mkcert localhost aaa.localhost 127.0.0.1.

MySQL server has gone away - in exactly 60 seconds

Increasing SQL-Wait-Timeout worked for me in this case, try this:

mysql_query("SET @@session.wait_timeout=900", $link);

before you first "normal" SQL queries.

How to format date string in java?

If you are looking for a solution to your particular case, it would be:

Date date = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'").parse("2012-05-20T09:00:00.000Z");
String formattedDate = new SimpleDateFormat("dd/MM/yyyy, Ka").format(date);

What are the differences and similarities between ffmpeg, libav, and avconv?

Confusing messages

These messages are rather misleading and understandably a source of confusion. Older Ubuntu versions used Libav which is a fork of the FFmpeg project. FFmpeg returned in Ubuntu 15.04 "Vivid Vervet".

The fork was basically a non-amicable result of conflicting personalities and development styles within the FFmpeg community. It is worth noting that the maintainer for Debian/Ubuntu switched from FFmpeg to Libav on his own accord due to being involved with the Libav fork.

The real ffmpeg vs the fake one

For a while both Libav and FFmpeg separately developed their own version of ffmpeg.

Libav then renamed their bizarro ffmpeg to avconv to distance themselves from the FFmpeg project. During the transition period the "not developed anymore" message was displayed to tell users to start using avconv instead of their counterfeit version of ffmpeg. This confused users into thinking that FFmpeg (the project) is dead, which is not true. A bad choice of words, but I can't imagine Libav not expecting such a response by general users.

This message was removed upstream when the fake "ffmpeg" was finally removed from the Libav source, but, depending on your version, it can still show up in Ubuntu because the Libav source Ubuntu uses is from the ffmpeg-to-avconv transition period.

In June 2012, the message was re-worded for the package libav - 4:0.8.3-0ubuntu0.12.04.1. Unfortunately the new "deprecated" message has caused additional user confusion.

Starting with Ubuntu 15.04 "Vivid Vervet", FFmpeg's ffmpeg is back in the repositories again.

libav vs Libav

To further complicate matters, Libav chose a name that was historically used by FFmpeg to refer to its libraries (libavcodec, libavformat, etc). For example the libav-user mailing list, for questions and discussions about using the FFmpeg libraries, is unrelated to the Libav project.

How to tell the difference

If you are using avconv then you are using Libav. If you are using ffmpeg you could be using FFmpeg or Libav. Refer to the first line in the console output to tell the difference: the copyright notice will either mention FFmpeg or Libav.

Secondly, the version numbering schemes differ. Each of the FFmpeg or Libav libraries contains a version.h header which shows a version number. FFmpeg will end in three digits, such as 57.67.100, and Libav will end in one digit such as 57.67.0. You can also view the library version numbers by running ffmpeg or avconv and viewing the console output.

If you want to use the real ffmpeg

Ubuntu 15.04 "Vivid Vervet" or newer

The real ffmpeg is in the repository, so you can install it with:

apt-get install ffmpeg

For older Ubuntu versions

Your options are:

These methods are non-intrusive, reversible, and will not interfere with the system or any repository packages.

Another possible option is to upgrade to Ubuntu 15.04 "Vivid Vervet" or newer and just use ffmpeg from the repository.

Also see

For an interesting blog article on the situation, as well as a discussion about the main technical differences between the projects, see The FFmpeg/Libav situation.

For files in directory, only echo filename (no path)

You can either use what SiegeX said above or if you aren't interested in learning/using parameter expansion, you can use:

for filename in $(ls /home/user/);
do
    echo $filename
done;

How to insert strings containing slashes with sed?

Great answer from Anonymous. \ solved my problem when I tried to escape quotes in HTML strings.

So if you use sed to return some HTML templates (on a server), use double backslash instead of single:

var htmlTemplate = "<div style=\\"color:green;\\"></div>";

How to make rpm auto install dependencies

In the case of openSUSE Leap 15, I'm receiving similar error:

> sudo rpm -i opera-stable_53.0.2907.68_amd64.rpm 
[sudo] password for root: 
warning: opera-stable_53.0.2907.68_amd64.rpm: Header V4 RSA/SHA512 Signature, key ID a5c7ff72: NOKEY
error: Failed dependencies:
    at is needed by opera-stable-53.0.2907.68-0.x86_64

I run this command to figure out what are the dependencies:

> sudo zypper install opera-stable_53.0.2907.68_amd64.rpm 
Loading repository data...
Reading installed packages...
Resolving package dependencies...

The following 4 NEW packages are going to be installed:
  at libfl2 libHX28 opera-stable

4 new packages to install.
Overall download size: 50.3 MiB. Already cached: 0 B. After the operation, additional 176.9 MiB will be used.
Continue? [y/n/...? shows all options] (y): n

Then I run this command to install dependencies:

> sudo zypper in at
Loading repository data...
Reading installed packages...
Resolving package dependencies...

The following 3 NEW packages are going to be installed:
  at libfl2 libHX28

3 new packages to install.
Overall download size: 208.6 KiB. Already cached: 0 B. After the operation, additional 600.4 KiB will be used.
Continue? [y/n/...? shows all options] (y): y

Then I run this to install the rpm file:

> sudo rpm -i opera-stable_53.0.2907.68_amd64.rpm

I'm not sure if it is the best practice, however it solved my issue.

How can I convert byte size into a human-readable format in Java?

Use an Android built-in class

For Android, there is a class, Formatter. Just one line of code and you are done.

android.text.format.Formatter.formatShortFileSize(activityContext, bytes);

It is like formatFileSize(), but trying to generate shorter numbers (showing fewer decimals).

android.text.format.Formatter.formatFileSize(activityContext, bytes);

It formats a content size to be in the form of bytes, kilobytes, megabytes, etc.

Update statement using with clause

If anyone comes here after me, this is the answer that worked for me.

NOTE: please make to read the comments before using this, this not complete. The best advice for update queries I can give is to switch to SqlServer ;)

update mytable t
set z = (
  with comp as (
    select b.*, 42 as computed 
    from mytable t 
    where bs_id = 1
  )
  select c.computed
  from  comp c
  where c.id = t.id
)

Good luck,

GJ

How to trigger button click in MVC 4

yo can try this code

@using (Html.BeginForm("SignUp", "Account", FormMethod.Post)){<fieldset>
    <legend>Sign Up</legend>
    <table>
        <tr>
            <td>
                @Html.Label("User Name")
            </td>
            <td>
                @Html.TextBoxFor(account => account.Username)
            </td>
        </tr>
        <tr>
            <td>
                @Html.Label("Email")
            </td>
            <td>
                @Html.TextBoxFor(account => account.Email)
            </td>
        </tr>
        <tr>
            <td>
                @Html.Label("Password")
            </td>
            <td>
                @Html.TextBoxFor(account => account.Password)
            </td>
        </tr>
        <tr>
            <td>
                @Html.Label("Confirm Password")
            </td>
            <td>
                @Html.Password("txtPassword")
            </td>
        </tr>
        <tr>
            <td>
                <input type="submit" name="btnSubmit" value="Sign Up" />
            </td>
        </tr>
    </table>
</fieldset>}

Can not run Java Applets in Internet Explorer 11 using JRE 7u51

For Windows 8.1 Users.... there is a little note on the java download site which says:

"Downloading and installing Java will only work in Desktop mode on Windows 8 and Windows 8.1. See the Java on Windows 8 FAQ for more detailed information."

Unfortunately, "Desktop mode" is not the default mode in Windows 8.1. After installing java and wasting 2hours trying to get java working with IE11, I went back to oracles site...paid a bit more attention to that warning!! switched to Desktop mode, and reinstalled java... hey presto it worked.

Furious, that java download does not work with the default config of Windows 8.1, don't know who to be more angry with? Oracle or Microsoft? ( or me for skimming over the warning..)

Create an enum with string values

//to access the enum with its string value you can convert it to object 
//then you can convert enum to object with proberty 
//for Example :

enum days { "one" =3, "tow", "Three" }

let _days: any = days;

if (_days.one == days.one)
{ 
    alert(_days.one + ' | ' + _days[4]);
}

How to display a date as iso 8601 format with PHP

For pre PHP 5:

function iso8601($time=false) {
    if(!$time) $time=time();
    return date("Y-m-d", $time) . 'T' . date("H:i:s", $time) .'+00:00';
}

Use Mockito to mock some methods but not others

What you want is org.mockito.Mockito.CALLS_REAL_METHODS according to the docs:

/**
 * Optional <code>Answer</code> to be used with {@link Mockito#mock(Class, Answer)}
 * <p>
 * {@link Answer} can be used to define the return values of unstubbed invocations.
 * <p>
 * This implementation can be helpful when working with legacy code.
 * When this implementation is used, unstubbed methods will delegate to the real implementation.
 * This is a way to create a partial mock object that calls real methods by default.
 * <p>
 * As usual you are going to read <b>the partial mock warning</b>:
 * Object oriented programming is more less tackling complexity by dividing the complexity into separate, specific, SRPy objects.
 * How does partial mock fit into this paradigm? Well, it just doesn't... 
 * Partial mock usually means that the complexity has been moved to a different method on the same object.
 * In most cases, this is not the way you want to design your application.
 * <p>
 * However, there are rare cases when partial mocks come handy: 
 * dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.)
 * However, I wouldn't use partial mocks for new, test-driven & well-designed code.
 * <p>
 * Example:
 * <pre class="code"><code class="java">
 * Foo mock = mock(Foo.class, CALLS_REAL_METHODS);
 *
 * // this calls the real implementation of Foo.getSomething()
 * value = mock.getSomething();
 *
 * when(mock.getSomething()).thenReturn(fakeValue);
 *
 * // now fakeValue is returned
 * value = mock.getSomething();
 * </code></pre>
 */

Thus your code should look like:

import org.junit.Test;
import static org.mockito.Mockito.*;
import static org.junit.Assert.*;

public class StockTest {

    public class Stock {
        private final double price;
        private final int quantity;

        Stock(double price, int quantity) {
            this.price = price;
            this.quantity = quantity;
        }

        public double getPrice() {
            return price;
        }

        public int getQuantity() {
            return quantity;
        }

        public double getValue() {
            return getPrice() * getQuantity();
        }
    }

    @Test
    public void getValueTest() {
        Stock stock = mock(Stock.class, withSettings().defaultAnswer(CALLS_REAL_METHODS));
        when(stock.getPrice()).thenReturn(100.00);
        when(stock.getQuantity()).thenReturn(200);
        double value = stock.getValue();

        assertEquals("Stock value not correct", 100.00 * 200, value, .00001);
    }
}

The call to Stock stock = mock(Stock.class); calls org.mockito.Mockito.mock(Class<T>) which looks like this:

 public static <T> T mock(Class<T> classToMock) {
    return mock(classToMock, withSettings().defaultAnswer(RETURNS_DEFAULTS));
}

The docs of the value RETURNS_DEFAULTS tell:

/**
 * The default <code>Answer</code> of every mock <b>if</b> the mock was not stubbed.
 * Typically it just returns some empty value. 
 * <p>
 * {@link Answer} can be used to define the return values of unstubbed invocations. 
 * <p>
 * This implementation first tries the global configuration. 
 * If there is no global configuration then it uses {@link ReturnsEmptyValues} (returns zeros, empty collections, nulls, etc.)
 */

No mapping found for HTTP request with URI [/WEB-INF/pages/apiForm.jsp]

I think I read the entire internet to figure out how to get sitemesh to handle my html paths without extension + API paths without extension. I was wrapped up in a straight jacket figuring this out, every turn seemed to break something else. Then I finally came upon this post.

<servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet>
    <servlet-name>jsp</servlet-name>
    <servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/*</url-pattern>
</servlet-mapping>

<servlet-mapping>
    <servlet-name>jsp</servlet-name>
    <url-pattern>/WEB-INF/views/*</url-pattern>
 </servlet-mapping>

<servlet-mapping>
    <servlet-name>jsp</servlet-name>
    <url-pattern>/WEB-INF/decorators/*</url-pattern>
</servlet-mapping>

Enter this in your dispatcher-servlet.xml

<mvc:default-servlet-handler/>

How can I get a list of all functions stored in the database of a particular schema in PostgreSQL?

If any one is interested here is what query is executed by psql on postgres 9.1:

SELECT n.nspname as "Schema",
  p.proname as "Name",
  pg_catalog.pg_get_function_result(p.oid) as "Result data type",
  pg_catalog.pg_get_function_arguments(p.oid) as "Argument data types",
 CASE
  WHEN p.proisagg THEN 'agg'
  WHEN p.proiswindow THEN 'window'
  WHEN p.prorettype = 'pg_catalog.trigger'::pg_catalog.regtype THEN 'trigger'
  ELSE 'normal'
 END as "Type"
FROM pg_catalog.pg_proc p
     LEFT JOIN pg_catalog.pg_namespace n ON n.oid = p.pronamespace
WHERE pg_catalog.pg_function_is_visible(p.oid)
      AND n.nspname <> 'pg_catalog'
      AND n.nspname <> 'information_schema'
ORDER BY 1, 2, 4;

You can get what psql runs for a backslash command by running psql with the -E flag.

How to select <td> of the <table> with javascript?

There are a lot of ways to accomplish this, and this is but one of them.

$("table").find("tbody td").eq(0).children().first()

How to find files modified in last x minutes (find -mmin does not work as expected)

this command may be help you sir

find -type f -mtime -60

How can I measure the similarity between two images?

How to measure similarity between two images entirely depends on what you would like to measure, for example: contrast, brightness, modality, noise... and then choose the best suitable similarity measure there is for you. You can choose from MAD (mean absolute difference), MSD (mean squared difference) which are good for measuring brightness...there is also available CR (correlation coefficient) which is good in representing correlation between two images. You could also choose from histogram based similarity measures like SDH (standard deviation of difference image histogram) or multimodality similarity measures like MI (mutual information) or NMI (normalized mutual information).

Because this similarity measures cost much in time, it is advised to scale images down before applying these measures on them.

Is there a way to get element by XPath using JavaScript in Selenium WebDriver?

In Chrome Dev Tools you can run the following:

$x("some xpath")

update listview dynamically with adapter

add and remove methods are easier to use. They update the data in the list and call notifyDataSetChanged in background.

Sample code:

adapter.add("your object");
adapter.remove("your object");

Update records using LINQ

You have two options as far as I know:

  1. Perform your query, iterate over it to modify the entities, then call SaveChanges().
  2. Execute a SQL command like you mentioned at the top of your question. To see how to do this, take a look at this page.

If you use option 2, you're losing some of the abstraction that the Entity Framework gives you, but if you need to perform a very large update, this might be the best choice for performance reasons.

what is the difference between XSD and WSDL

XSD defines a schema which is a definition of how an XML document can be structured. You can use it to check that a given XML document is valid and follows the rules you've laid out in the schema.

WSDL is a XML document that describes a web service. It shows which operations are available and how data should be structured to send to those operations.

WSDL documents have an associated XSD that show what is valid to put in a WSDL document.

JavaScript - Getting HTML form values

<input type="text" id="note_text" />

let value = document.getElementById("note_text").value;

Get cart item name, quantity all details woocommerce

Note on product price

The price of the product in the cart may be different from that of the product.

This can happen when you use some plugins that change the price of the product when it is added to the cart or if you have added a custom function in the functions.php of your active theme.

If you want to be sure you get the price of the product added to the cart you will have to get it like this:

foreach ( WC()->cart->get_cart() as $cart_item ) {
    // gets the cart item quantity
    $quantity           = $cart_item['quantity'];
    // gets the cart item subtotal
    $line_subtotal      = $cart_item['line_subtotal']; 
    $line_subtotal_tax  = $cart_item['line_subtotal_tax'];
    // gets the cart item total
    $line_total         = $cart_item['line_total'];
    $line_tax           = $cart_item['line_tax'];
    // unit price of the product
    $item_price         = $line_subtotal / $quantity;
    $item_tax           = $line_subtotal_tax / $quantity;

}

Instead of:

foreach ( WC()->cart->get_cart() as $cart_item ) {
    // gets the product object
    $product            = $cart_item['data'];
    // gets the product prices
    $regular_price      = $product->get_regular_price();
    $sale_price         = $product->get_sale_price();
    $price              = $product->get_price();
}

Other data you can get:

foreach ( WC()->cart->get_cart() as $cart_item ) {

    // get the data of the cart item
    $product_id         = $cart_item['product_id'];
    $variation_id       = $cart_item['variation_id'];

    // gets the cart item quantity
    $quantity           = $cart_item['quantity'];
    // gets the cart item subtotal
    $line_subtotal      = $cart_item['line_subtotal']; 
    $line_subtotal_tax  = $cart_item['line_subtotal_tax'];
    // gets the cart item total
    $line_total         = $cart_item['line_total'];
    $line_tax           = $cart_item['line_tax'];
    // unit price of the product
    $item_price         = $line_subtotal / $quantity;
    $item_tax           = $line_subtotal_tax / $quantity;

    // gets the product object
    $product            = $cart_item['data'];
    // get the data of the product
    $sku                = $product->get_sku();
    $name               = $product->get_name();
    $regular_price      = $product->get_regular_price();
    $sale_price         = $product->get_sale_price();
    $price              = $product->get_price();
    $stock_qty          = $product->get_stock_quantity();
    // attributes
    $attributes         = $product->get_attributes();
    $attribute          = $product->get_attribute( 'pa_attribute-name' ); // // specific attribute eg. "pa_color"
    // custom meta
    $custom_meta        = $product->get_meta( '_custom_meta_key', true );
    // product categories
    $categories         = wc_get_product_category_list(  $product->get_id() ); // returns a string with all product categories separated by a comma
}

app.config for a class library

You do want to add App.config to your tests class library, if you're using a tracer/logger. Otherwise nothing gets logged when you run the test through a test runner such as TestDriven.Net.

For example, I use TraceSource in my programs, but running tests doesn't log anything unless I add an App.config file with the trace/log configuration to the test class library too.

Otherwise, adding App.config to a class library doesn't do anything.

Control flow in T-SQL SP using IF..ELSE IF - are there other ways?

CASE expression
      WHEN value1 THEN result1
      WHEN value2 THEN result2
      ...
      WHEN valueN THEN resultN

      [
        ELSE elseResult
      ]
END

http://www.4guysfromrolla.com/webtech/102704-1.shtml For more information.

How to decompile an APK or DEX file on Android platform?

Also you can use Android Multitool. You can make minor changes in the app like hiding GUI elements or modifying small part of Logic and rebuild the apk. Its easy to use and decompile/recompile apk and jar files. Here is the Link you can checkout.

Cheers

shorthand If Statements: C#

Recently, I really enjoy shorthand if else statements as a swtich case replacement. In my opinion, this is better in read and take less place. Just take a look:

var redirectUrl =
      status == LoginStatusEnum.Success ? "/SecretPage"
    : status == LoginStatusEnum.Failure ? "/LoginFailed"
    : status == LoginStatusEnum.Sms ? "/2-StepSms"
    : status == LoginStatusEnum.EmailNotConfirmed ? "/EmailNotConfirmed"
    : "/404-Error";

instead of

string redirectUrl;
switch (status)
{
    case LoginStatusEnum.Success:
        redirectUrl = "/SecretPage";
        break;
    case LoginStatusEnum.Failure:
        redirectUrl = "/LoginFailed";
        break;
    case LoginStatusEnum.Sms:
        redirectUrl = "/2-StepSms";
        break;
    case LoginStatusEnum.EmailNotConfirmed:
        redirectUrl = "/EmailNotConfirmed";
        break;
    default:
        redirectUrl = "/404-Error";
        break;
}

Java array reflection: isArray vs. instanceof

getClass().isArray() is significantly slower on Sun Java 5 or 6 JRE than on IBM.

So much that using clazz.getName().charAt(0) == '[' is faster on Sun JVM.

How to convert buffered image to image and vice-versa?

Example: say you have an 'image' you want to scale you will need a bufferedImage probably, and probably will be starting out with just 'Image' object. So this works I think... The AVATAR_SIZE is the target width we want our image to be:

Image imgData = image.getScaledInstance(Constants.AVATAR_SIZE, -1, Image.SCALE_SMOOTH);     

BufferedImage bufferedImage = new BufferedImage(imgData.getWidth(null), imgData.getHeight(null), BufferedImage.TYPE_INT_RGB);

bufferedImage.getGraphics().drawImage(imgData, 0, 0, null);

jQuery OR Selector?

Use a comma.

'.classA, .classB'

You may choose to omit the space.

Combine two columns of text in pandas dataframe

more efficient is

def concat_df_str1(df):
    """ run time: 1.3416s """
    return pd.Series([''.join(row.astype(str)) for row in df.values], index=df.index)

and here is a time test:

import numpy as np
import pandas as pd

from time import time


def concat_df_str1(df):
    """ run time: 1.3416s """
    return pd.Series([''.join(row.astype(str)) for row in df.values], index=df.index)


def concat_df_str2(df):
    """ run time: 5.2758s """
    return df.astype(str).sum(axis=1)


def concat_df_str3(df):
    """ run time: 5.0076s """
    df = df.astype(str)
    return df[0] + df[1] + df[2] + df[3] + df[4] + \
           df[5] + df[6] + df[7] + df[8] + df[9]


def concat_df_str4(df):
    """ run time: 7.8624s """
    return df.astype(str).apply(lambda x: ''.join(x), axis=1)


def main():
    df = pd.DataFrame(np.zeros(1000000).reshape(100000, 10))
    df = df.astype(int)

    time1 = time()
    df_en = concat_df_str4(df)
    print('run time: %.4fs' % (time() - time1))
    print(df_en.head(10))


if __name__ == '__main__':
    main()

final, when sum(concat_df_str2) is used, the result is not simply concat, it will trans to integer.

Display unescaped HTML in Vue.js

You can read that here

If you use

{{<br />}}

it'll be escaped. If you want raw html, you gotta use

{{{<br />}}}

EDIT (Feb 5 2017): As @hitautodestruct points out, in vue 2 you should use v-html instead of triple curly braces.

How to get span tag inside a div in jQuery and assign a text?

Try this

$("#message span").text("hello world!");

function Errormessage(txt) {
    var elem = $("#message");
    elem.fadeIn("slow");
    // find the span inside the div and assign a text
    elem.children("span").text("your text");

    elem.children("a.close-notify").click(function() {
        elem.fadeOut("slow");
    });
}

How do I register a .NET DLL file in the GAC?

As ando said, just drag and drop the assembly to the C:\windows\assembly folder. It works.

Clicking URLs opens default browser

The method boolean shouldOverrideUrlLoading(WebView view, String url) was deprecated in API 24. If you are supporting new devices you should use boolean shouldOverrideUrlLoading (WebView view, WebResourceRequest request).

You can use both by doing something like this:

if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
    newsItem.setWebViewClient(new WebViewClient() {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
            view.loadUrl(request.getUrl().toString());
            return true;
        }
    });
} else {
    newsItem.setWebViewClient(new WebViewClient() {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;
        }
    });
}

Why am I getting this redefinition of class error?

You define the class gameObject in both your .cpp file and your .h file.
That is creating a redefinition error.

You should define the class, ONCE, in ONE place. (convention says the definition is in the .h, and all the implementation is in the .cpp)

Please help us understand better, what part of the error message did you have trouble with?

The first part of the error says the class has been redefined in gameObject.cpp
The second part of the error says the previous definition is in gameObject.h.

How much clearer could the message be?

Pad a number with leading zeros in JavaScript

Not a lot of "slick" going on so far:

function pad(n, width, z) {
  z = z || '0';
  n = n + '';
  return n.length >= width ? n : new Array(width - n.length + 1).join(z) + n;
}

When you initialize an array with a number, it creates an array with the length set to that value so that the array appears to contain that many undefined elements. Though some Array instance methods skip array elements without values, .join() doesn't, or at least not completely; it treats them as if their value is the empty string. Thus you get a copy of the zero character (or whatever "z" is) between each of the array elements; that's why there's a + 1 in there.

Example usage:

pad(10, 4);      // 0010
pad(9, 4);       // 0009
pad(123, 4);     // 0123

pad(10, 4, '-'); // --10

Broken references in Virtualenvs

All the answers are great here, I tried a couple of solutions mentioned above by Ryan, Chris and couldn't resolve the issue, so had to follow a quick and dirty way.

  1. rm -rf <project dir> (or mv <project dir> <backup projct dir> if you want to keep a backup)
  2. git clone <project git url>
  3. Move on!

Nothing novel here, but it makes life easier!

Function overloading in Python: Missing

Now, unless you're trying to write C++ code using Python syntax, what would you need overloading for?

I think it's exactly opposite. Overloading is only necessary to make strongly-typed languages act more like Python. In Python you have keyword argument, and you have *args and **kwargs.

See for example: What is a clean, Pythonic way to have multiple constructors in Python?

How to send an email with Gmail as provider using Python?

I ran into a similar problem and stumbled on this question. I got an SMTP Authentication Error but my user name / pass was correct. Here is what fixed it. I read this:

https://support.google.com/accounts/answer/6010255

In a nutshell, google is not allowing you to log in via smtplib because it has flagged this sort of login as "less secure", so what you have to do is go to this link while you're logged in to your google account, and allow the access:

https://www.google.com/settings/security/lesssecureapps

Once that is set (see my screenshot below), it should work.

enter image description here

Login now works:

smtpserver = smtplib.SMTP("smtp.gmail.com", 587)
smtpserver.ehlo()
smtpserver.starttls()
smtpserver.ehlo()
smtpserver.login('[email protected]', 'me_pass')

Response after change:

(235, '2.7.0 Accepted')

Response prior:

smtplib.SMTPAuthenticationError: (535, '5.7.8 Username and Password not accepted. Learn more at\n5.7.8 http://support.google.com/mail/bin/answer.py?answer=14257 g66sm2224117qgf.37 - gsmtp')

Still not working? If you still get the SMTPAuthenticationError but now the code is 534, its because the location is unknown. Follow this link:

https://accounts.google.com/DisplayUnlockCaptcha

Click continue and this should give you 10 minutes for registering your new app. So proceed to doing another login attempt now and it should work.

UPDATE: This doesn't seem to work right away you may be stuck for a while getting this error in smptlib:

235 == 'Authentication successful'
503 == 'Error: already authenticated'

The message says to use the browser to sign in:

SMTPAuthenticationError: (534, '5.7.9 Please log in with your web browser and then try again. Learn more at\n5.7.9 https://support.google.com/mail/bin/answer.py?answer=78754 qo11sm4014232igb.17 - gsmtp')

After enabling 'lesssecureapps', go for a coffee, come back, and try the 'DisplayUnlockCaptcha' link again. From user experience, it may take up to an hour for the change to kick in. Then try the sign-in process again.

git: fatal: Could not read from remote repository

In my case I was using an ssh key with a password to authenticate with github. I hadn't set up pageant properly in Windows (only in cygwin). The missing steps were to point the git_ssh environment variable to plink.exe. Also, you need to get github.com into the plink known_hosts.

   plink github.com
   y
   <then ctrl-c>

Hope this helps!

I sure wish intellij would have given me a more useful error, or better yet asked me to type in the ssh key password.

Check if a number is int or float

variable.isnumeric checks if a value is an integer:

 if myVariable.isnumeric:
    print('this varibale is numeric')
 else:
    print('not numeric')

Calling a phone number in swift

Okay I got help and figured it out. Also I put in a nice little alert system just in case the phone number is not valid. My issue was I was calling it right but the number had spaces and unwanted characters such as ("123 456-7890"). UIApplication only works or accepts if your number is ("1234567890"). So you basically remove the space and invalid characters by making a new variable to pull only the numbers. Then calls those numbers with the UIApplication.

func callSellerPressed (sender: UIButton!){
        var newPhone = ""

        for (var i = 0; i < countElements(busPhone); i++){

            var current:Int = i
            switch (busPhone[i]){
                case "0","1","2","3","4","5","6","7","8","9" : newPhone = newPhone + String(busPhone[i])
                default : println("Removed invalid character.")
            }
        }

        if  (busPhone.utf16Count > 1){

        UIApplication.sharedApplication().openURL(NSURL(string: "tel://" + newPhone)!)
        }
        else{
            let alert = UIAlertView()
            alert.title = "Sorry!"
            alert.message = "Phone number is not available for this business"
            alert.addButtonWithTitle("Ok")
                alert.show()
        }
        }

Should I URL-encode POST data?

@DougW has clearly answered this question, but I still like to add some codes here to explain Doug's points. (And correct errors in the code above)

Solution 1: URL-encode the POST data with a content-type header :application/x-www-form-urlencoded .

Note: you do not need to urlencode $_POST[] fields one by one, http_build_query() function can do the urlencoding job nicely.

$fields = array(
    'mediaupload'=>$file_field,
    'username'=>$_POST["username"],
    'password'=>$_POST["password"],
    'latitude'=>$_POST["latitude"],
    'longitude'=>$_POST["longitude"],
    'datetime'=>$_POST["datetime"],
    'category'=>$_POST["category"],
    'metacategory'=>$_POST["metacategory"],
    'caption'=>$_POST["description"]
);

$fields_string = http_build_query($fields);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_POST,1);
curl_setopt($ch, CURLOPT_POSTFIELDS,$fields_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$response = curl_exec($ch);

Solution 2: Pass the array directly as the post data without URL-encoding, while the Content-Type header will be set to multipart/form-data.

$fields = array(
        'mediaupload'=>$file_field,
        'username'=>$_POST["username"],
        'password'=>$_POST["password"],
        'latitude'=>$_POST["latitude"],
        'longitude'=>$_POST["longitude"],
        'datetime'=>$_POST["datetime"],
        'category'=>$_POST["category"],
        'metacategory'=>$_POST["metacategory"],
        'caption'=>$_POST["description"]
    );

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL,$url);
    curl_setopt($ch, CURLOPT_POST,1);
    curl_setopt($ch, CURLOPT_POSTFIELDS,$fields);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    $response = curl_exec($ch);

Both code snippets work, but using different HTTP headers and bodies.

How to center body on a page?

For those that do know the width, you could do something like

div {
     max-width: ???px; //px,%
     margin-left:auto;
     margin-right:auto;
}

I also agree about not setting text-align:center on the body because it can mess up the rest of your code and you might have to individually set text-align:left on a lot of things either then or in the future.

Get a substring of a char*

You can use strstr. Example code here.

Note that the returned result is not null terminated.

Reading From A Text File - Batch

Your code "for /f "tokens=* delims=" %%x in (a.txt) do echo %%x" will work on most Windows Operating Systems unless you have modified commands.

So you could instead "cd" into the directory to read from before executing the "for /f" command to follow out the string. For instance if the file "a.txt" is located at C:\documents and settings\%USERNAME%\desktop\a.txt then you'd use the following.

cd "C:\documents and settings\%USERNAME%\desktop"
for /f "tokens=* delims=" %%x in (a.txt) do echo %%x
echo.
echo.
echo.
pause >nul
exit

But since this doesn't work on your computer for x reason there is an easier and more efficient way of doing this. Using the "type" command.

@echo off
color a
cls
cd "C:\documents and settings\%USERNAME%\desktop"
type a.txt
echo.
echo.
pause >nul
exit

Or if you'd like them to select the file from which to write in the batch you could do the following.

@echo off
:A
color a
cls
echo Choose the file that you want to read.
echo.
echo.
tree
echo.
echo.
echo.
set file=
set /p file=File:
cls
echo Reading from %file%
echo.
type %file%
echo.
echo.
echo.
set re=
set /p re=Y/N?:
if %re%==Y goto :A
if %re%==y goto :A
exit

SQL how to check that two tables has exactly the same data?

SELECT c.ID
FROM clients c
WHERE EXISTS(SELECT c2.ID 
FROM clients2 c2
WHERE c2.ID = c.ID);

Will return all ID's that are the SAME in both tables. To get the differences change EXISTS to NOT EXISTS.

Using IF..ELSE in UPDATE (SQL server 2005 and/or ACCESS 2007)

Yes you can use CASE

UPDATE table 
SET columnB = CASE fieldA 
        WHEN columnA=1 THEN 'x' 
        WHEN columnA=2 THEN 'y' 
        ELSE 'z' 
      END 
WHERE columnC = 1

How to detect if CMD is running as Administrator/has elevated privileges?

Pretty much what others have put before, but as a one liner that can be put at the beginning of a batch command. (Well, usually after @echo off.)

net.exe session 1>NUL 2>NUL || (Echo This script requires elevated rights. & Exit /b 1)

How can I disable a tab inside a TabControl?

The only way is to catch the Selecting event and prevent a tab from being activated.

org.apache.tomcat.util.bcel.classfile.ClassFormatException: Invalid byte tag in constant pool: 15

This issue is happening because you have installed jre1.8.0_101-1.8.0_101-fcs.i58.rpm as well jdk-1.7.0_80-fcs.x86_64.rpm. so just uninstall your jre rpm & restart your application. It should work out.

Message: Trying to access array offset on value of type null

This happens because $cOTLdata is not null but the index 'char_data' does not exist. Previous versions of PHP may have been less strict on such mistakes and silently swallowed the error / notice while 7.4 does not do this anymore.

To check whether the index exists or not you can use isset():

isset($cOTLdata['char_data'])

Which means the line should look something like this:

$len = isset($cOTLdata['char_data']) ? count($cOTLdata['char_data']) : 0;

Note I switched the then and else cases of the ternary operator since === null is essentially what isset already does (but in the positive case).

"This project is incompatible with the current version of Visual Studio"

For me, I got this same error in VS 2015 and just installed the VS 2015 update 1, though from another answer, VS is actually up to Update 3, now (after which, they got the error and had to install .NET Core). Had issues when it hit certain packages, like the Windows SDK ones, and had to point the installer back at the paths in my original CD, and for some, even that didn't work and had to skip them and re-download from an internet-connected computer, transfer them over, and run them later manually (computer was not connected to the internet to be able to download updated versions of the packages), but after doing all that and doing a reboot, the error was gone and my project loaded fine.

How to select all instances of selected region in Sublime Text

Note: You should not edit the default settings, because they get reset on updates/upgrades. For customization, you should override any setting by using the user bindings.

On Mac:

  • Sublime Text 2 > Preferences > Key Bindings-Default
  • Sublime Text 3 > Preferences > Key Bindings

This opens a document that you can edit the keybindings for Sublime.

If you search "ctrl+super+g" you find this:

{ "keys": ["ctrl+super+g"], "command": "find_all_under" },

How to merge multiple dicts with same key or different key?

A compact possibility

d1={'a':1,'b':2}
d2={'c':3,'d':4}
context={**d1, **d2}
context
{'b': 2, 'c': 3, 'd': 4, 'a': 1}

How can I export tables to Excel from a webpage

This code is IE only so it is only useful in situations where you know all of your users will be using IE (like, for example, in some corporate environments.)

<script Language="javascript">
function ExportHTMLTableToExcel()
{
   var thisTable = document.getElementById("tbl").innerHTML;
   window.clipboardData.setData("Text", thisTable);
   var objExcel = new ActiveXObject ("Excel.Application");
   objExcel.visible = true;

   var objWorkbook = objExcel.Workbooks.Add;
   var objWorksheet = objWorkbook.Worksheets(1);
   objWorksheet.Paste;
}
</script>

apache mod_rewrite is not working or not enabled

Try setting: "AllowOverride All".

Forbidden :You don't have permission to access /phpmyadmin on this server

You could simply go to phpmyadmin.conf file and change "deny from all" to "allow from all". Well it worked for me, hope it works for you as well.

How to resolve TypeError: Cannot convert undefined or null to object

Below snippet is sufficient to understand how I encountered the same issue but in a different scenario and how I solved it using the guidance in the accepted answer. In my case I was trying to log the keys of object present in the 0th index of the 'defaultViewData' array using Object.keys() method.

defaultViewData = [{"name": "DEFAULT_VIEW_PLP","value": {"MSH25": "LIST"}}] 

console.log('DEFAULT_VIEW', Object.keys(this.props.defaultViewData[0]));

The console.log was not getting printed and I was getting the same error as posted in this question. To prevent that error I added below condition

    if(this.props.defaultViewData[0]) {
  console.log('DEFAULT_VIEW', Object.keys(this.props.defaultViewData[0]));
}

Adding this check ensured that I didn't get this error. I hope this helps for someone.

Note: This is React.js code. (although to understand the problem it doesn't matter).

How to print spaces in Python?

To print any amount of lines between printed text use:

print("Hello" + '\n' *insert number of whitespace lines+ "World!")

'\n' can be used to make whitespace, multiplied, it will make multiple whitespace lines.

How to get all selected values of a multiple select box?

ES6

[...select.options].filter(option => option.selected).map(option => option.value)

Where select is a reference to the <select> element.

To break it down:

  • [...select.options] takes the Array-like list of options and destructures it so that we can use Array.prototype methods on it (Edit: also consider using Array.from())
  • filter(...) reduces the options to only the ones that are selected
  • map(...) converts the raw <option> elements into their respective values

return in for loop or outside loop

Now someone told me that this is not very good programming because I use the return statement inside a loop and this would cause garbage collection to malfunction.

That's a bunch of rubbish. Everything inside the method would be cleaned up unless there were other references to it in the class or elsewhere (a reason why encapsulation is important). As a rule of thumb, it's generally better to use one return statement simply because it is easier to figure out where the method will exit.

Personally, I would write:

Boolean retVal = false;
for(int i=0; i<array.length; ++i){
    if(array[i]==valueToFind) {
        retVal = true;
        break; //Break immediately helps if you are looking through a big array
    }
}
return retVal;

Convert array of strings into a string in Java

You could do this, given an array a of primitive type:

StringBuffer result = new StringBuffer();
for (int i = 0; i < a.length; i++) {
   result.append( a[i] );
   //result.append( optional separator );
}
String mynewstring = result.toString();

Equivalent function for DATEADD() in Oracle

Not my answer :

I wasn't too happy with the answers above and some additional searching yielded this :

SELECT SYSDATE AS current_date,

       SYSDATE + 1 AS plus_1_day,

       SYSDATE + 1/24 AS plus_1_hours,

       SYSDATE + 1/24/60 AS plus_1_minutes,

       SYSDATE + 1/24/60/60 AS plus_1_seconds

FROM   dual;

which I found very helpful. From http://sqlbisam.blogspot.com/2014/01/add-date-interval-to-date-or-dateadd.html

Passing parameters to click() & bind() event in jquery?

An alternative for the bind() method.

Use the click() method, do something like this:

commentbtn.click({id: 10, name: "João"}, onClickCommentBtn);

function onClickCommentBtn(event)
{
  alert("Id=" + event.data.id + ", Name = " + event.data.name);
}

Or, if you prefer:

commentbtn.click({id: 10, name: "João"},  function (event) {
  alert("Id=" + event.data.id + ", Nome = " + event.data.name);
});

It will show an alert box with the following infos:

Id = 10, Name = João

How to utilize date add function in Google spreadsheet?

=TO_DATE(TO_PURE_NUMBER(Insert Date cell, i.e. AM4)+[how many days to add in numbers, e.g. 3 days])

Looks like in practice:

=TO_DATE(TO_PURE_NUMBER(AM4)+3)

Essentially you are converting the date into a pure number and back into a date again.

How can I check if a single character appears in a string?

String.contains(String) or String.indexOf(String) - suggested

"abc".contains("Z"); // false - correct
"zzzz".contains("Z"); // false - correct
"Z".contains("Z"); // true - correct
"and".contains(""); // true - correct
"and".contains(""); // false - correct
"and".indexOf(""); // 0 - correct
"and".indexOf(""); // -1 - correct

String.indexOf(int) and carefully considered String.indexOf(char) with char to int widening

"and".indexOf("".charAt(0)); // 0 though incorrect usage has correct output due to portion of correct data
"and".indexOf("".charAt(0)); // 0 -- incorrect usage and ambiguous result
"and".indexOf("".codePointAt(0)); // -1 -- correct usage and correct output

The discussions around character is ambiguous in Java world

can the value of char or Character considered as single character?

No. In the context of unicode characters, char or Character can sometimes be part of a single character and should not be treated as a complete single character logically.

if not, what should be considered as single character (logically)?

Any system supporting character encodings for Unicode characters should consider unicode's codepoint as single character.

So Java should do that very clear & loud rather than exposing too much of internal implementation details to users.

String class is bad at abstraction (though it requires confusingly good amount of understanding of its encapsulations to understand the abstraction and hence an anti-pattern).

How is it different from general char usage?

char can be only be mapped to a character in Basic Multilingual Plane.

Only codePoint - int can cover the complete range of Unicode characters.

Why is this difference?

char is internally treated as 16-bit unsigned value and could not represent all the unicode characters using UTF-16 internal representation using only 2-bytes. Sometimes, values in a 16-bit range have to be combined with another 16-bit value to correctly define character.

Without getting too verbose, the usage of indexOf, charAt, length and such methods should be more explicit. Sincerely hoping Java will add new UnicodeString and UnicodeCharacter classes with clearly defined abstractions.

Reason to prefer contains and not indexOf(int)

  1. Practically there are many code flows that treat a logical character as char in java.
  2. In Unicode context, char is not sufficient
  3. Though the indexOf takes in an int, char to int conversion masks this from the user and user might do something like str.indexOf(someotherstr.charAt(0))(unless the user is aware of the exact context)
  4. So, treating everything as CharSequence (aka String) is better
    public static void main(String[] args) {
        System.out.println("and".indexOf("".charAt(0))); // 0 though incorrect usage has correct output due to portion of correct data
        System.out.println("and".indexOf("".charAt(0))); // 0 -- incorrect usage and ambiguous result
        System.out.println("and".indexOf("".codePointAt(0))); // -1 -- correct usage and correct output
        System.out.println("and".contains("")); // true - correct
        System.out.println("and".contains("")); // false - correct
    }

Where do I put my php files to have Xampp parse them?

The default location to put all the web projects in ubuntu with LAMPP is :

 /var/www/

You may make symbolic link to public_html directory from this directory.Refered. Hope this is helpful.

How to log cron jobs?

cron already sends the standard output and standard error of every job it runs by mail to the owner of the cron job.

You can use MAILTO=recipient in the crontab file to have the emails sent to a different account.

For this to work, you need to have mail working properly. Delivering to a local mailbox is usually not a problem (in fact, chances are ls -l "$MAIL" will reveal that you have already been receiving some) but getting it off the box and out onto the internet requires the MTA (Postfix, Sendmail, what have you) to be properly configured to connect to the world.

If there is no output, no email will be generated.

A common arrangement is to redirect output to a file, in which case of course the cron daemon won't see the job return any output. A variant is to redirect standard output to a file (or write the script so it never prints anything - perhaps it stores results in a database instead, or performs maintenance tasks which simply don't output anything?) and only receive an email if there is an error message.

To redirect both output streams, the syntax is

42 17 * * * script >>stdout.log 2>>stderr.log

Notice how we append (double >>) instead of overwrite, so that any previous job's output is not replaced by the next one's.

As suggested in many answers here, you can have both output streams be sent to a single file; replace the second redirection with 2>&1 to say "standard error should go wherever standard output is going". (But I don't particularly endorse this practice. It mainly makes sense if you don't really expect anything on standard output, but may have overlooked something, perhaps coming from an external tool which is called from your script.)

cron jobs run in your home directory, so any relative file names should be relative to that. If you want to write outside of your home directory, you obviously need to separately make sure you have write access to that destination file.

A common antipattern is to redirect everything to /dev/null (and then ask Stack Overflow to help you figure out what went wrong when something is not working; but we can't see the lost output, either!)

From within your script, make sure to keep regular output (actual results, ideally in machine-readable form) and diagnostics (usually formatted for a human reader) separate. In a shell script,

echo "$results"  # regular results go to stdout
echo "$0: something went wrong" >&2

Some platforms (and e.g. GNU Awk) allow you to use the file name /dev/stderr for error messages, but this is not properly portable; in Perl, warn and die print to standard error; in Python, write to sys.stderr, or use logging; in Ruby, try $stderr.puts. Notice also how error messages should include the name of the script which produced the diagnostic message.

Is there a way to take a screenshot using Java and save it to some sort of image?

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File; 
import javax.imageio.ImageIO;
import javax.swing.*;  

public class HelloWorldFrame extends JFrame implements ActionListener {

JButton b;
public HelloWorldFrame() {
    this.setVisible(true);
    this.setLayout(null);
    b = new JButton("Click Here");
    b.setBounds(380, 290, 120, 60);
    b.setBackground(Color.red);
    b.setVisible(true);
    b.addActionListener(this);
    add(b);
    setSize(1000, 700);
}
public void actionPerformed(ActionEvent e)
{
    if (e.getSource() == b) 
    {
        this.dispose();
        try {
            Thread.sleep(1000);
            Toolkit tk = Toolkit.getDefaultToolkit(); 
            Dimension d = tk.getScreenSize();
            Rectangle rec = new Rectangle(0, 0, d.width, d.height);  
            Robot ro = new Robot();
            BufferedImage img = ro.createScreenCapture(rec);
            File f = new File("myimage.jpg");//set appropriate path
            ImageIO.write(img, "jpg", f);
        } catch (Exception ex) {
            System.out.println(ex.getMessage());
        }
    }
}

public static void main(String[] args) {
    HelloWorldFrame obj = new HelloWorldFrame();
}
}

How do I set specific environment variables when debugging in Visual Studio?

Set up a batch file which you can invoke. Pass the path the batch file, and have the batch file set the environment variable and then invoke NUnit.

Get all rows from SQLite

try:

Cursor  cursor = db.rawQuery("select * from table",null);

AND for List<String>:

if (cursor.moveToFirst()) {
  while (!cursor.isAfterLast()) {
    String name = cursor.getString(cursor.getColumnIndex(countyname));

    list.add(name);
    cursor.moveToNext();
  }
}

How to exclude *AutoConfiguration classes in Spring Boot JUnit tests?

@SpringBootTest(classes = {Application.class}
              , webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT
              , properties="spring.autoconfigure.exclude=com.xx.xx.AutoConfiguration"
               )

ref:https://github.com/spring-projects/spring-boot/issues/8579

What does this GCC error "... relocation truncated to fit..." mean?

On Cygwin -mcmodel=medium is already default and doesn't help. To me adding -Wl,--image-base -Wl,0x10000000 to GCC linker did fixed the error.

How to tell git to use the correct identity (name and email) for a given project?

If you don't use the --global parameter it will set the variables for the current project only.

Why is json_encode adding backslashes?

json_encode will always add slashes.

Check some examples on the manual HERE

This is because if there are some characters which needs to escaped then they will create problem.

To use the json please Parse your json to ensure that the slashes are removed

Well whether or not you remove slashesthe json will be parsed without any problem by eval.

<?php
$array = array('url'=>'http://mysite.com/uploads/gallery/7f/3b/f65ab8165d_logo.jpeg','id'=>54);
?>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script type="text/javascript">
var x = jQuery.parseJSON('<?php echo json_encode($array);?>');
alert(x);
</script>

This is my code and i m able to parse the JSON.

Check your code May be you are missing something while parsing the JSON

Select columns from result set of stored procedure

(Assuming SQL Server)

The only way to work with the results of a stored procedure in T-SQL is to use the INSERT INTO ... EXEC syntax. That gives you the option of inserting into a temp table or a table variable and from there selecting the data you need.

What is the difference between Views and Materialized Views in Oracle?

View: View is just a named query. It doesn't store anything. When there is a query on view, it runs the query of the view definition. Actual data comes from table.

Materialised views: Stores data physically and get updated periodically. While querying MV, it gives data from MV.

How to add "Maven Managed Dependencies" library in build path eclipse?

from the command line type:

mvn eclipse:eclipse

this will add all the dependencies you have in your pom.xml into eclipse...

however, if you haven't done any of this before you may need to do one other, one time only step.

Close eclipse, then run the following command from the shell:

mvn -Declipse.workspace=<eclipse workspace> eclipse:add-maven-repo

sample:

mvn -Declipse.workspace=/home/ft/workspaces/wksp1/ eclipse:add-maven-repo

Validate form field only on submit or user input

If you want to show error messages on form submission, you can use condition form.$submitted to check if an attempt was made to submit the form. Check following example.

<form name="myForm" novalidate ng-submit="myForm.$valid && createUser()">
  <input type="text" name="name" ng-model="user.name" placeholder="Enter name of user" required>
  <div ng-messages="myForm.name.$error" ng-if="myForm.$submitted">
    <div ng-message="required">Please enter user name.</div>
  </div>

  <input type="text" name="address" ng-model="user.address" placeholder="Enter Address" required ng-maxlength="30">
  <div ng-messages="myForm.name.$error" ng-if="myForm.$submitted">
    <div ng-message="required">Please enter user address.</div>
    <div ng-message="maxlength">Should be less than 30 chars</div>
  </div>

  <button type="submit">
    Create user
  </button>
</form>

How do I get the result of a command in a variable in windows?

You should use the for command, here is an example:

@echo off
rem Commands go here
exit /b
:output
for /f "tokens=* useback" %%a in (`%~1`) do set "output=%%a"

and you can use call :output "Command goes here" then the output will be in the %output% variable.

Note: If you have a command output that is multiline, this tool will set the output to the last line of your multiline command.

TLS 1.2 not working in cURL

TLS 1.1 and TLS 1.2 are supported since OpenSSL 1.0.1

Forcing TLS 1.1 and 1.2 are only supported since curl 7.34.0

You should consider an upgrade.

Using subprocess to run Python script on Windows

You are using a pathname separator which is platform dependent. Windows uses "\" and Unix uses "/".

Using true and false in C

I don't know you specific situation. Back when I was writing C programs, we have always used #2.

#define FALSE = 0
#define TRUE = !FALSE

This might be otherwise under alien platform to DOS or Intel-based processors. But I used to use both C and ASM together writing graphic libraries and graphical IDE. I was a true fan of Micheal Abrash and was intending to learn about texture mapping and so. Anyway! That's not the subject of the question here!

This was the most commonly used form to define boolean values in C, as this headerfile stdbool.h did not exist then.

fatal: ambiguous argument 'origin': unknown revision or path not in the working tree

I ran into the same situation where commands such as git diff origin or git diff origin master produced the error reported in the question, namely Fatal: ambiguous argument...

To resolve the situation, I ran the command

git symbolic-ref refs/remotes/origin/HEAD refs/remotes/origin/master

to set refs/remotes/origin/HEAD to point to the origin/master branch.

Before running this command, the output of git branch -a was:

* master
  remotes/origin/master

After running the command, the error no longer happened and the output of git branch -a was:

* master
  remotes/origin/HEAD -> origin/master
  remotes/origin/master

(Other answers have already identified that the source of the error is HEAD not being set for origin. But I thought it helpful to provide a command which may be used to fix the error in question, although it may be obvious to some users.)


Additional information:

For anybody inclined to experiment and go back and forth between setting and unsetting refs/remotes/origin/HEAD, here are some examples.

To unset:
git remote set-head origin --delete

To set:
(additional ways, besides the way shown at the start of this answer)
git remote set-head origin master to set origin/head explicitly
OR
git remote set-head origin --auto to query the remote and automatically set origin/HEAD to the remote's current branch.

References:

  • This SO Answer
  • This SO Comment and its associated answer
  • git remote --help see set-head description
  • git symbolic-ref --help

Angular, Http GET with parameter?

An easy and usable way to solve this problem

getGetSuppor(filter): Observale<any[]> {
   return this.https.get<any[]>('/api/callCenter/getSupport' + '?' + this.toQueryString(filter));
}

private toQueryString(query): string {
   var parts = [];
   for (var property in query) {
     var value = query[propery];
     if (value != null && value != undefined)
        parts.push(encodeURIComponent(propery) + '=' + encodeURIComponent(value))
   }
   
   return parts.join('&');
}

How to prevent null values inside a Map and null fields inside a bean from getting serialized through Jackson

For Jackson versions < 2.0 use this annotation on the class being serialized:

@JsonSerialize(include=JsonSerialize.Inclusion.NON_NULL)

Is calling destructor manually always a sign of bad design?

Found another example where you would have to call destructor(s) manually. Suppose you have implemented a variant-like class that holds one of several types of data:

struct Variant {
    union {
        std::string str;
        int num;
        bool b;
    };
    enum Type { Str, Int, Bool } type;
};

If the Variant instance was holding a std::string, and now you're assigning a different type to the union, you must destruct the std::string first. The compiler will not do that automatically.

Accessing JSON object keys having spaces

The way to do this is via the bracket notation.

_x000D_
_x000D_
var test = {_x000D_
    "id": "109",_x000D_
    "No. of interfaces": "4"_x000D_
}_x000D_
alert(test["No. of interfaces"]);
_x000D_
_x000D_
_x000D_

For more info read out here:

All possible array initialization syntaxes

In case you want to initialize a fixed array of pre-initialized equal (non-null or other than default) elements, use this:

var array = Enumerable.Repeat(string.Empty, 37).ToArray();

Also please take part in this discussion.

How to install APK from PC?

  1. Connect Android device to PC via USB cable and turn on USB storage.
  2. Copy .apk file to attached device's storage.
  3. Turn off USB storage and disconnect it from PC.
  4. Check the option Settings ? Applications ? Unknown sources OR Settings > Security > Unknown Sources.
  5. Open FileManager app and click on the copied .apk file. If you can't fine the apk file try searching or allowing hidden files. It will ask you whether to install this app or not. Click Yes or OK.

This procedure works even if ADB is not available.

postgresql - sql - count of `true` values

Cast the Boolean to an integer and sum.

SELECT count(*),sum(myCol::int);

You get 6,3.

How to install a certificate in Xcode (preparing for app store submission)

These instructions are for XCode 6.4 (since I couldn't find the update for the recent versions even this was a bit outdated)

a) Part on the developers' website:

Sign in into: https://developer.apple.com/

Member Center

Certificates, Identifiers & Profiles

Certificates>All

Click "+" to add, and then follow the instructions. You will need to open "Keychain Access.app", there under "Keychain Access" menu > "Certificate Assistant>", choose "Request a Certificate From a Certificate Authority" etc.

b) XCode part:

After all, you need to go to XCode, and open XCode>Preferences..., choose your Apple ID > View Details... > click that rounded arrow to update as well as "+" to check for iOS Distribution or iOS Developer Signing Identities.

How can I switch themes in Visual Studio 2012

Tools -> Options ->Environment -> General

Or use new Quick Launch to open Options Use Quick Launch to open Options

enter image description here

For more themes, download Microsoft Visual Studio 2012 Color Theme Editor for more themes including good old VS2010 theme.

Look at this video for a demo.

Web-scraping JavaScript page with Python

You'll want to use urllib, requests, beautifulSoup and selenium web driver in your script for different parts of the page, (to name a few).
Sometimes you'll get what you need with just one of these modules.
Sometimes you'll need two, three, or all of these modules.
Sometimes you'll need to switch off the js on your browser.
Sometimes you'll need header info in your script.
No websites can be scraped the same way and no website can be scraped in the same way forever without having to modify your crawler, usually after a few months. But they can all be scraped! Where there's a will there's a way for sure.
If you need scraped data continuously into the future just scrape everything you need and store it in .dat files with pickle.
Just keep searching how to try what with these modules and copying and pasting your errors into the Google.

Setting font on NSAttributedString on UITextView disregards line spacing

//For proper line spacing

NSString *text1 = @"Hello";
NSString *text2 = @"\nWorld";
UIFont *text1Font = [UIFont fontWithName:@"HelveticaNeue-Medium" size:10];
NSMutableAttributedString *attributedString1 =
[[NSMutableAttributedString alloc] initWithString:text1 attributes:@{ NSFontAttributeName : text1Font }];
NSMutableParagraphStyle *paragraphStyle1 = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle1 setAlignment:NSTextAlignmentCenter];
[paragraphStyle1 setLineSpacing:4];
[attributedString1 addAttribute:NSParagraphStyleAttributeName value:paragraphStyle1 range:NSMakeRange(0, [attributedString1 length])];

UIFont *text2Font = [UIFont fontWithName:@"HelveticaNeue-Medium" size:16];
NSMutableAttributedString *attributedString2 =
[[NSMutableAttributedString alloc] initWithString:text2 attributes:@{NSFontAttributeName : text2Font }];
NSMutableParagraphStyle *paragraphStyle2 = [[NSMutableParagraphStyle alloc] init];
[paragraphStyle2 setLineSpacing:4];
[paragraphStyle2 setAlignment:NSTextAlignmentCenter];
[attributedString2 addAttribute:NSParagraphStyleAttributeName value:paragraphStyle2 range:NSMakeRange(0, [attributedString2 length])];

[attributedString1 appendAttributedString:attributedString2];

How to validate a file upload field using Javascript/jquery

Check it's value property:

In jQuery (since your tag mentions it):

$('#fileInput').val()

Or in vanilla JavaScript:

document.getElementById('myFileInput').value

How to change column datatype in SQL database without losing data

Alter column data type with check type of column :

IF EXISTS(
       SELECT 1
       FROM   sys.columns
       WHERE  NAME = 'YourColumnName'
              AND [object_id] = OBJECT_ID('dbo.YourTable')
              AND TYPE_NAME(system_type_id) = 'int'
   )
    ALTER TABLE dbo.YourTable ALTER COLUMN YourColumnName BIT

Table is marked as crashed and should be repaired

This means your MySQL table is corrupted and you need to repair it. Use

myisamchk -r /DB_NAME/wp_posts

from the command line. While you running the repair you should shut down your website temporarily so that no new connections are attempted to your database while its being repaired.

toggle show/hide div with button?

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$('#hideshow').click(function(){
    $('#content').toggle('show');
  });
});
</script>

And the html

<div id='content'>Hello World</div>
<input type='button' id='hideshow' value='hide/show'>

Extension exists but uuid_generate_v4 fails

If you've changed the search_path, specify the public schema in the function call:

public.uuid_generate_v4()

How to get ALL child controls of a Windows Forms form of a specific type (Button/Textbox)?

Don't forget that you can also have a TextBox within other controls other than container controls too. You can even add a TextBox to a PictureBox.

So you also need to check if

someControl.HasChildren = True

in any recursive function.

This is the result I had from a layout to test this code:

TextBox13   Parent = Panel5
TextBox12   Parent = Panel5
TextBox9   Parent = Panel2
TextBox8   Parent = Panel2
TextBox16   Parent = Panel6
TextBox15   Parent = Panel6
TextBox14   Parent = Panel6
TextBox10   Parent = Panel3
TextBox11   Parent = Panel4
TextBox7   Parent = Panel1
TextBox6   Parent = Panel1
TextBox5   Parent = Panel1
TextBox4   Parent = Form1
TextBox3   Parent = Form1
TextBox2   Parent = Form1
TextBox1   Parent = Form1
tbTest   Parent = myPicBox

Try this with one Button and one RichTextBox on a form.

Option Strict On
Option Explicit On
Option Infer Off

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim pb As New PictureBox
        pb.Name = "myPicBox"
        pb.BackColor = Color.Goldenrod
        pb.Size = New Size(100, 100)
        pb.Location = New Point(0, 0)
        Dim tb As New TextBox
        tb.Name = "tbTest"
        pb.Controls.Add(tb)
        Me.Controls.Add(pb)

        Dim textBoxList As New List(Of Control)
        textBoxList = GetAllControls(Of TextBox)(Me)

        Dim sb As New System.Text.StringBuilder
        For index As Integer = 0 To textBoxList.Count - 1
            sb.Append(textBoxList.Item(index).Name & "   Parent = " & textBoxList.Item(index).Parent.Name & System.Environment.NewLine)
        Next

        RichTextBox1.Text = sb.ToString
    End Sub

    Private Function GetAllControls(Of T)(ByVal searchWithin As Control) As List(Of Control)

        Dim returnList As New List(Of Control)

        If searchWithin.HasChildren = True Then
            For Each ctrl As Control In searchWithin.Controls
                If TypeOf ctrl Is T Then
                    returnList.Add(ctrl)
                End If
                returnList.AddRange(GetAllControls(Of T)(ctrl))
            Next
        ElseIf searchWithin.HasChildren = False Then
            For Each ctrl As Control In searchWithin.Controls
                If TypeOf ctrl Is T Then
                    returnList.Add(ctrl)
                End If
                returnList.AddRange(GetAllControls(Of T)(ctrl))
            Next
        End If
        Return returnList
    End Function

End Class

Is it possible to install iOS 6 SDK on Xcode 5?

  • Download Xcode 4.6.x from the Apple Dev Center: https://developer.apple.com/downloads/index.action
  • Create a folder called Xcode4 within the Applications folder and drag-n-drop the downloaded dmg there.
  • Open a terminal window

    $sudo cp -R /Applications/Xcode4/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS6.1.sdk /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/
    
  • You will be prompt to enter a password since you're inside a system folder

  • Open Xcode 5 and you should now see both SDKs

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{table}
\begin{tabular}{| p{5cm} | p{5cm} | p{5cm} |}
  -- cut --
\end{tabular}
\caption{My table}
\label{table:kysymys}
\end{table}

Table \ref{table:kysymys} on page \pageref{table:kysymys} refers to the ...

How to check if array element is null to avoid NullPointerException in Java

You can do it on one line of code (without array declaration):

object[] someArray = new object[] 
{
    "aaaa",
    3,
    null
};
bool containsSomeNull = someArray.Any(x => x == null);

Resolving require paths with webpack

resolve.alias should work exactly the way you described, so I'm providing this as an answer to help mitigate any confusion that may result from the suggestion in the original question that it does not work.

a resolve configuration like the one below will give you the desired results:

// used to resolve absolute path to project's root directory (where web pack.config.js should be located)
var path = require( 'path' );
...
{
  ...
  resolve: {
    // add alias for application code directory
    alias:{
      mydir: path.resolve( __dirname, 'path', 'to', 'mydir' )
    },
    extensions: [ '', '.js' ]
  }
}

require( 'mydir/myfile.js' ) will work as expected. If it does not, there must be some other issue.

If you have multiple modules that you want to add to the search path, resolve.root makes sense, but if you just want to be able to reference components within your application code without relative paths, alias seems to be the most straight-forward and explicit.

An important advantage of alias is that it gives you the opportunity to namespace your requires which can add clarity to your code; just like it is easy to see from other requires what module is being referenced, alias allows you to write descriptive requires that make it obvious you're requiring internal modules, e.g. require( 'my-project/component' ). resolve.root just plops you into the desired directory without giving you the opportunity to namespace it further.

Reload .profile in bash shell script (in unix)?

Try this to reload your current shell:

source ~/.profile

Adding horizontal spacing between divs in Bootstrap 3

From what I understand you want to make a navigation bar or something similar to it. What I recommend doing is making a list and editing the items from there. Just try this;

<ul>
    <li class='item col-md-12 panel' id='gameplay-title'>Title</li>
    <li class='item col-md-6 col-md-offset-3 panel' id='gameplay-scoreboard'>Scoreboard</li>
</ul>

And so on... To add more categories add another ul in there. Now, for the CSS you just need this;

ul {
    list-style: none;
}
.item {
    display: inline;
    padding-right: 20px;
}

How to fix the height of a <div> element?

If you want to keep the height of the DIV absolute, regardless of the amount of text inside use the following:

overflow: hidden;

How to get length of a list of lists in python

You can do it with reduce:

a = [[1, 2, 3], [4, 5, 6], [7, 8, 9], [], [1, 2]]
print(reduce(lambda count, l: count + len(l), a, 0))
# result is 11

SQL Server: converting UniqueIdentifier to string in a case statement

In my opinion, uniqueidentifier / GUID is neither a varchar nor an nvarchar but a char(36). Therefore I use:

CAST(xyz AS char(36))

Simulating Key Press C#

You can use the Win32 API FindWindow or FindWindowEx to find the window handle of the open browser and then just call SendMessage with WM_KEYDOWN. Typically it's easiest just to pass the window caption to FindWindowEx and have it find the associated window handle for you.

If you are starting the browser process yourself via a Process process object then you can use process.MainWindowHandle instead of calling FindWindowEx.

Spy++ is a very useful tool when you want to start working with other windows. It basically allows you to learn another program's hierarchy of UI elements. You can also monitor all of the messages that go into the window you're monitoring. I have more info in this thread.

The F5 keystroke has this virtual key code:

const int VK_F5 = 0x74;

The p/invoke signature for FindWindowEx in C# is:

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

You can p/invoke (bring in) the Win32 API SendMessage like this:

[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

So to recap, you call FindWindowEx directly from your C# code after having the above code somewhere inside your class. FindWindowEx will return a window handle. Then once you have the window handle, you can send any keystroke(s) to the window, or call many other Win32 API calls on the window handle. Or even find a child window by using another call to FindWindowEx. For example you could select the edit control of the browser even and then change it's text.

If all else goes wrong and you think you're sending the right key to the window, you can use spy++ to see what messages are sent to the window when you manually set focus to the browser and manually press F5.

Git push/clone to new server

There are many ways to move repositories around, git bundle is a nice way if you have insufficient network availability. Since a Git repository is really just a directory full of files, you can "clone" a repository by making a copy of the .git directory in whatever way suits you best.

The most efficient way is to use an external repository somewhere (use GitHub or set up Gitosis), and then git push.

Ctrl+click doesn't work in Eclipse Juno

I was facing the same issue in eclipse. I verified preferences and build path and also no error. Tried closing and opening the eclipse but nothing worked. Even I could not run debug configuration. I created a new workspace and Ctrl+click / ?+click (Mac os) was working fine.

Hope this may help someone.

How do I check if string contains substring?

Returns number of times the keyword is included in the string.

var count = "I have one keyword".match(/keyword/g);
var clean_count = !count ? false : count.length;

JQuery to load Javascript file dynamically

I realize I am a little late here, (5 years or so), but I think there is a better answer than the accepted one as follows:

$("#addComment").click(function() {
    if(typeof TinyMCE === "undefined") {
        $.ajax({
            url: "tinymce.js",
            dataType: "script",
            cache: true,
            success: function() {
                TinyMCE.init();
            }
        });
    }
});

The getScript() function actually prevents browser caching. If you run a trace you will see the script is loaded with a URL that includes a timestamp parameter:

http://www.yoursite.com/js/tinymce.js?_=1399055841840

If a user clicks the #addComment link multiple times, tinymce.js will be re-loaded from a differently timestampped URL. This defeats the purpose of browser caching.

===

Alternatively, in the getScript() documentation there is a some sample code that demonstrates how to enable caching by creating a custom cachedScript() function as follows:

jQuery.cachedScript = function( url, options ) {

    // Allow user to set any option except for dataType, cache, and url
    options = $.extend( options || {}, {
        dataType: "script",
        cache: true,
        url: url
    });

    // Use $.ajax() since it is more flexible than $.getScript
    // Return the jqXHR object so we can chain callbacks
    return jQuery.ajax( options );
};

// Usage
$.cachedScript( "ajax/test.js" ).done(function( script, textStatus ) {
    console.log( textStatus );
});

===

Or, if you want to disable caching globally, you can do so using ajaxSetup() as follows:

$.ajaxSetup({
    cache: true
});

Preventing scroll bars from being hidden for MacOS trackpad users in WebKit/Blink

The appearance of the scroll bars can be controlled with WebKit's -webkit-scrollbar pseudo-elements [blog]. You can disable the default appearance and behaviour by setting -webkit-appearance [docs] to none.

Because you're removing the default style, you'll also need to specify the style yourself or the scroll bar will never show up. The following CSS recreates the appearance of the hiding scroll bars:

Example (jsfiddle)

CSS
.frame::-webkit-scrollbar {
    -webkit-appearance: none;
}

.frame::-webkit-scrollbar:vertical {
    width: 11px;
}

.frame::-webkit-scrollbar:horizontal {
    height: 11px;
}

.frame::-webkit-scrollbar-thumb {
    border-radius: 8px;
    border: 2px solid white; /* should match background, can't be transparent */
    background-color: rgba(0, 0, 0, .5);
}

.frame::-webkit-scrollbar-track { 
    background-color: #fff; 
    border-radius: 8px; 
} 
WebKit (Chrome) Screenshot

screenshot showing webkit's scrollbar, without needing to hover

How to get table cells evenly spaced?

In your CSS file:

.TableHeader { width: 100px; }

This will set all of the td tags below each header to 100px. You can also add a width definition (in the markup) to each individual th tag, but the above solution would be easier.

Calling a java method from c++ in Android

If it's an object method, you need to pass the object to CallObjectMethod:

jobject result = env->CallObjectMethod(obj, messageMe, jstr);

What you were doing was the equivalent of jstr.messageMe().

Since your is a void method, you should call:

env->CallVoidMethod(obj, messageMe, jstr);

If you want to return a result, you need to change your JNI signature (the ()V means a method of void return type) and also the return type in your Java code.

Xcode 4 - "Archive" is greyed out?

You have to select the device in the schemes menu in the top left where you used to select between simulator/device. It won’t let you archive a build for the simulator.

Or you may find that if the iOS device is already selected the archive box isn’t selected when you choose “Edit Schemes” => “Build”.

Looping over a list in Python

Try this,

x in mylist is better and more readable than x in mylist[:] and your len(x) should be equal to 3.

>>> mylist = [[1,2,3],[4,5,6,7],[8,9,10]]
>>> for x in mylist:
...      if len(x)==3:
...        print x
...
[1, 2, 3]
[8, 9, 10]

or if you need more pythonic use list-comprehensions

>>> [x for x in mylist if len(x)==3]
[[1, 2, 3], [8, 9, 10]]
>>>

Most efficient way to reverse a numpy array

Because this seems to not be marked as answered yet... The Answer of Thomas Arildsen should be the proper one: just use

np.flipud(your_array) 

if it is a 1d array (column array).

With matrizes do

fliplr(matrix)

if you want to reverse rows and flipud(matrix) if you want to flip columns. No need for making your 1d column array a 2dimensional row array (matrix with one None layer) and then flipping it.

Reading a simple text file

In Mono For Android....

try
{
    System.IO.Stream StrIn = this.Assets.Open("MyMessage.txt");
    string Content = string.Empty;
    using (System.IO.StreamReader StrRead = new System.IO.StreamReader(StrIn))
    {
      try
      {
            Content = StrRead.ReadToEnd();
            StrRead.Close();
      }  
      catch (Exception ex) { csFunciones.MostarMsg(this, ex.Message); }
      }
          StrIn.Close();
          StrIn = null;
}
catch (Exception ex) { csFunciones.MostarMsg(this, ex.Message); }

How to upload image in CodeIgniter?

Below code for an uploading a single file at a time. This is correct and perfect to upload a single file. Read all commented instructions and follow the code. Definitely, it is worked.

public function upload_file() {
    ***// Upload folder location***
    $config['upload_path'] = './public/upload/';

    ***// Allowed file type***
    $config['allowed_types'] = 'jpg|jpeg|png|pdf';

    ***// Max size, i will set 2MB***
    $config['max_size'] = '2024';

    $config['max_width'] = '1024';
    $config['max_height'] = '768';

    ***// load upload library***            
    $this->load->library('upload', $config);

    ***// do_upload is the method, to send the particular image and file on that 
       // particular 
       // location that is detail in $config['upload_path']. 
       // In bracks will set name upload, here you need to set input name attribute 
       // value.***

    if($this->upload->do_upload('upload')) {
       $data = $this->upload->data();
       $post['upload'] = $data['file_name'];
    } else {
      $error = array('error' => $this->upload->display_errors());
    }
 }

Why does a base64 encoded string have an = sign at the end

http://www.hcidata.info/base64.htm

Encoding "Mary had" to Base 64

In this example we are using a simple text string ("Mary had") but the principle holds no matter what the data is (e.g. graphics file). To convert each 24 bits of input data to 32 bits of output, Base 64 encoding splits the 24 bits into 4 chunks of 6 bits. The first problem we notice is that "Mary had" is not a multiple of 3 bytes - it is 8 bytes long. Because of this, the last group of bits is only 4 bits long. To remedy this we add two extra bits of '0' and remember this fact by putting a '=' at the end. If the text string to be converted to Base 64 was 7 bytes long, the last group would have had 2 bits. In this case we would have added four extra bits of '0' and remember this fact by putting '==' at the end.

How do I print the type or class of a variable in Swift?

Swift 3.0

let string = "Hello"
let stringArray = ["one", "two"]
let dictionary = ["key": 2]

print(type(of: string)) // "String"

// Get type name as a string
String(describing: type(of: string)) // "String"
String(describing: type(of: stringArray)) // "Array<String>"
String(describing: type(of: dictionary)) // "Dictionary<String, Int>"

// Get full type as a string
String(reflecting: type(of: string)) // "Swift.String"
String(reflecting: type(of: stringArray)) // "Swift.Array<Swift.String>"
String(reflecting: type(of: dictionary)) // "Swift.Dictionary<Swift.String, Swift.Int>"

How to programmatically disable page scrolling with jQuery

You can attach a function to scroll events and prevent its default behaviour.

var $window = $(window);

$window.on("mousewheel DOMMouseScroll", onMouseWheel);

function onMouseWheel(e) {
    e.preventDefault();
}

https://jsfiddle.net/22cLw9em/

In Angular, how to redirect with $location.path as $http.post success callback

it's very easy code .. but hard to fined..

detailsApp.controller("SchoolCtrl", function ($scope, $location) { 
      $scope.addSchool = function () {

        location.href='/ManageSchool/TeacherProfile?ID=' + $scope.TeacherID;
      }
});

Replace non ASCII character from string

This will search and replace all non ASCII letters:

String resultString = subjectString.replaceAll("[^\\x00-\\x7F]", "");

How to get client IP address using jQuery

jQuery can handle JSONP, just pass an url formatted with the callback=? parameter to the $.getJSON method, for example:

_x000D_
_x000D_
$.getJSON("https://api.ipify.org/?format=json", function(e) {_x000D_
    console.log(e.ip);_x000D_
});
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
_x000D_
_x000D_
_x000D_

This example is of a really simple JSONP service implemented on with api.ipify.org.

If you aren't looking for a cross-domain solution the script can be simplified even more, since you don't need the callback parameter, and you return pure JSON.

How to set an iframe src attribute from a variable in AngularJS

Please remove call to trustSrc function and try again like this . {{trustSrc(currentProject.url)}} to {{currentProject.url}}. Check this link http://plnkr.co/edit/caqS1jE9fpmMn5NofUve?p=preview


But according to the Angular Js 1.2 Documentation, you should write a function for getting src url. Have a look on the following code.

Before:

Javascript

scope.baseUrl = 'page';
scope.a = 1;
scope.b = 2;

Html

<!-- Are a and b properly escaped here? Is baseUrl controlled by user? -->
<iframe src="{{baseUrl}}?a={{a}&b={{b}}"

But for security reason they are recommending following method

Javascript

var baseUrl = "page";
scope.getIframeSrc = function() {

  // One should think about their particular case and sanitize accordingly
  var qs = ["a", "b"].map(function(value, name) {
      return encodeURIComponent(name) + "=" +
             encodeURIComponent(value);
    }).join("&");

  // `baseUrl` isn't exposed to a user's control, so we don't have to worry about escaping it.
  return baseUrl + "?" + qs;
};

Html

<iframe src="{{getIframeSrc()}}">

How to Exit a Method without Exiting the Program?

I would use return null; to indicate that there is no data to be returned

Automatically set appsettings.json for dev and release environments in asp.net core?

Just an update for .NET core 2.0 users, you can specify application configuration after the call to CreateDefaultBuilder:

public class Program
{
   public static void Main(string[] args)
   {
      BuildWebHost(args).Run();
   }

   public static IWebHost BuildWebHost(string[] args) =>
      WebHost.CreateDefaultBuilder(args)
             .ConfigureAppConfiguration(ConfigConfiguration)
             .UseStartup<Startup>()
             .Build();

   static void ConfigConfiguration(WebHostBuilderContext ctx, IConfigurationBuilder config)
   {
            config.SetBasePath(Directory.GetCurrentDirectory())
                .AddJsonFile("config.json", optional: false, reloadOnChange: true)
                .AddJsonFile($"config.{ctx.HostingEnvironment.EnvironmentName}.json", optional: true, reloadOnChange: true);

   }
 }

Session state can only be used when enableSessionState is set to true either in a configuration

Following answer from below given path worked fine.

I found a solution that worked perfectly! Add the following to web.config:

<system.webServer>
<modules>
<!-- UrlRewriter code here -->
<remove name="Session" />
<add name="Session" type="System.Web.SessionState.SessionStateModule" preCondition="" />
</modules>
</system.webServer>

Hope this helps someone else!

json_encode/json_decode - returns stdClass instead of Array in PHP

Although, as mentioned, you could add a second parameter here to indicate you want an array returned:

$array = json_decode($json, true);

Many people might prefer to cast the results instead:

$array = (array)json_decode($json);

It might be more clear to read.

Date in mmm yyyy format in postgresql

You can write your select query as,

select * from table_name where to_char(date_time_column, 'YYYY-MM')  = '2011-03';

How to fix Error: this class is not key value coding-compliant for the key tableView.'

Any chance that you changed the name of your table view from "tableView" to "myTableView" at some point?

How to list all available Kafka brokers in a cluster?

If you are using new version of Kafka e.g. 5.3.3, you can use

kafka-broker-api-versions  --bootstrap-server BROKER | grep 9092

You just need to pass one of the brokers

How do I Set Background image in Flutter?

body: Container(
    decoration: BoxDecoration(
      image: DecorationImage(
        image: AssetImage('images/background.png'),fit:BoxFit.cover
      )
    ),
);

How to grey out a button?

Set Clickable as false and change the backgroung color as:

callButton.setClickable(false);
callButton.setBackgroundColor(Color.parseColor("#808080"));

Controlling number of decimal digits in print output in R

One more solution able to control the how many decimal digits to print out based on needs (if you don't want to print redundant zero(s))

For example, if you have a vector as elements and would like to get sum of it

elements <- c(-1e-05, -2e-04, -3e-03, -4e-02, -5e-01, -6e+00, -7e+01, -8e+02)
sum(elements)
## -876.5432

Apparently, the last digital as 1 been truncated, the ideal result should be -876.54321, but if set as fixed printing decimal option, e.g sprintf("%.10f", sum(elements)), redundant zero(s) generate as -876.5432100000

Following the tutorial here: printing decimal numbers, if able to identify how many decimal digits in the certain numeric number, like here in -876.54321, there are 5 decimal digits need to print, then we can set up a parameter for format function as below:

decimal_length <- 5
formatC(sum(elements), format = "f", digits = decimal_length)
## -876.54321

We can change the decimal_length based on each time query, so it can satisfy different decimal printing requirement.

How to list active connections on PostgreSQL?

Following will give you active connections/ queries in postgres DB-

SELECT 
    pid
    ,datname
    ,usename
    ,application_name
    ,client_hostname
    ,client_port
    ,backend_start
    ,query_start
    ,query
    ,state
FROM pg_stat_activity
WHERE state = 'active';

You may use 'idle' instead of active to get already executed connections/queries.

Break string into list of characters in Python

Because strings are (immutable) sequences they can be unpacked similar to lists:

with open(filename, 'rU') as fd:
    multiLine = fd.read()
    *lst, = multiLine

When running map(lambda x: x, multiLine) this is clearly more efficient, but in fact it returns a map object instead of a list.

with open(filename, 'rU') as fd:
    multiLine = fd.read()
    list(map(lambda x: x, multiLine))

Turning the map object into a list will take longer than the unpacking method.

Convert String to System.IO.Stream

this is old but for help :

you can also use the stringReader stream

string str = "asasdkopaksdpoadks";
StringReader TheStream = new StringReader( str );

Detecting iOS orientation change instantly

Try making your changes in:

- (void) viewWillLayoutSubviews {}

The code will run at every orientation change as the subviews get laid out again.

Can you have if-then-else logic in SQL?

Please check whether this helps:

select TOP 1
    product, 
    price 
from 
    table1 
where 
    (project=1 OR Customer=2 OR company=3) AND
    price IS NOT NULL
ORDER BY company 

How to set value to variable using 'execute' in t-sql?

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Andrew Foster
-- Create date: 28 Mar 2013
-- Description: Allows the dynamic pull of any column value up to 255 chars from regUsers table
-- =============================================
ALTER PROCEDURE dbo.PullTableColumn
(
    @columnName varchar(255),
    @id int
)
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    DECLARE @columnVal TABLE (columnVal nvarchar(255));

    DECLARE @sql nvarchar(max);
    SET @sql = 'SELECT ' + @columnName + ' FROM regUsers WHERE id=' + CAST(@id AS varchar(10));
    INSERT @columnVal EXEC sp_executesql @sql;

    SELECT * FROM @columnVal;
END
GO

how do I create an infinite loop in JavaScript

You can also use a while loop:

while (true) {
    //your code
}

CSS Cell Margin

Apply this to your first <td>:

padding-right:10px;

HTML example:

<table>
   <tr>
      <td style="padding-right:10px">data</td>
      <td>more data</td>
   </tr>
</table>

SQL Server ORDER BY date and nulls last

I know this is old but this is what worked for me

Order by Isnull(Date,'12/31/9999')

UnicodeEncodeError: 'ascii' codec can't encode character u'\u2013' in position 3 2: ordinal not in range(128)

I had the same problem. This work fine for me:

str(objdata).encode('utf-8')

Make text wrap in a cell with FPDF?

Text Wrap:

The MultiCell is used for print text with multiple lines. It has the same atributes of Cell except for ln and link.

$pdf->MultiCell( 200, 40, $reportSubtitle, 1);

Line Height:

What multiCell does is to spread the given text into multiple cells, this means that the second parameter defines the height of each line (individual cell) and not the height of all cells (collectively).

MultiCell(float w, float h, string txt [, mixed border [, string align [, boolean fill]]])

You can read the full documentation here.

The name 'InitializeComponent' does not exist in the current context

I just encountered this problem, and it turned out to be that my project is stored in my user folder, which is stored on the network, and we had a momentary network outage. I did a build; it complained that my files had been modified outside the editor (they hadn't; the file locks just got borked), and it built fine, removing the error regarding the InitializeComponent() method.

BTW, in case you're wondering, developing something from a network drive is bad practice. It becomes particularly problematic when you're trying to leverage .NET's managed code; in my experience, it freaks out every time you build. I forgot to put this little throw-away project in the proper folder, and ended up paying the price.

Perform Segue programmatically and pass parameters to the destination view

I understand the problem of performing the segue at one place and maintaining the state to send parameters in prepare for segue.

I figured out a way to do this. I've added a property called userInfoDict to ViewControllers using a category. and I've override perform segue with identifier too, in such a way that If the sender is self(means the controller itself). It will pass this userInfoDict to the next ViewController.

Here instead of passing the whole UserInfoDict you can also pass the specific params, as sender and override accordingly.

1 thing you need to keep in mind. don't forget to call super method in ur performSegue method.

Angular.js and HTML5 date input value -- how to get Firefox to show a readable date value in a date input?

Check this fully functional directive for MEAN.JS (Angular.js, bootstrap, Express.js and MongoDb)

Based on @Blackhole ´s response, we just finished it to be used with mongodb and express.

It will allow you to save and load dates from a mongoose connector

Hope it Helps!!

angular.module('myApp')
.directive(
  'dateInput',
  function(dateFilter) {
    return {
      require: 'ngModel',
      template: '<input type="date" class="form-control"></input>',
      replace: true,
      link: function(scope, elm, attrs, ngModelCtrl) {
        ngModelCtrl.$formatters.unshift(function (modelValue) {
          return dateFilter(modelValue, 'yyyy-MM-dd');
        });

        ngModelCtrl.$parsers.push(function(modelValue){
           return angular.toJson(modelValue,true)
          .substring(1,angular.toJson(modelValue).length-1);
        })

      }
    };
  });

The JADE/HTML:

div(date-input, ng-model="modelDate")

How to create a DateTime equal to 15 minutes ago?

only the below code in Python 3.7 worked for me

from datetime import datetime,timedelta    
print(datetime.now()-timedelta(seconds=900))

SQL use CASE statement in WHERE IN clause

According to my Scenario, I did "use CASE statement in WHERE IN clause" like following

@AdjType varchar(20) = 'Value', 
@Base varchar(20) = 'Common'
where 
(select CASE WHEN SA.IsPersentage = 0 THEN 'Value' 
       WHEN SA.IsPersentage = 1 THEN 'Presentage' END) Like @AdjType
and (Select CASE WHEN SA.IsDependOnBasicSalary = 0 THEN 'Common' 
        WHEN SA.IsDependOnBasicSalary = 1 THEN 'Basic Salary' END) like @Base

JSON string to JS object

You can use this library from JSON.org to translate your string into a JSON object.

var var1_obj = JSON.parse(var1);

Or you can use the jquery-json library as well.

var var1_obj = $.toJSON(var1);

How to find topmost view controller on iOS

- (UIViewController*)topViewController {
    return [self topViewControllerWithRootViewController:[UIApplication sharedApplication].keyWindow.rootViewController];
}

- (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController {
    if ([rootViewController isKindOfClass:[UITabBarController class]]) {
        UITabBarController* tabBarController = (UITabBarController*)rootViewController;
        return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
    } else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
        UINavigationController* navigationController = (UINavigationController*)rootViewController;
        return [self topViewControllerWithRootViewController:navigationController.visibleViewController];
    } else if (rootViewController.presentedViewController) {
        UIViewController* presentedViewController = rootViewController.presentedViewController;
        return [self topViewControllerWithRootViewController:presentedViewController];
    } else {
        return rootViewController;
    }
}

What is newline character -- '\n'

From the sed man page:

Normally, sed cyclically copies a line of input, not including its terminating newline character, into a pattern space, (unless there is something left after a "D" function), applies all of the commands with addresses that select that pattern space, copies the pattern space to the standard output, appending a newline, and deletes the pattern space.

It's operating on the line without the newline present, so the pattern you have there can't ever match. You need to do something else - like match against $ (end-of-line) or ^ (start-of-line).

Here's an example of something that worked for me:

$ cat > states
California
Massachusetts
Arizona
$ sed -e 's/$/\
> /' states
California

Massachusetts

Arizona

I typed a literal newline character after the \ in the sed line.

HTML - Change\Update page contents without refreshing\reloading the page

You've got the right idea, so here's how to go ahead: the onclick handlers run on the client side, in the browser, so you cannot call a PHP function directly. Instead, you need to add a JavaScript function that (as you mentioned) uses AJAX to call a PHP script and retrieve the data. Using jQuery, you can do something like this:

<script type="text/javascript">
function recp(id) {
  $('#myStyle').load('data.php?id=' + id);
}
</script>

<a href="#" onClick="recp('1')" > One   </a>
<a href="#" onClick="recp('2')" > Two   </a>
<a href="#" onClick="recp('3')" > Three </a>

<div id='myStyle'>
</div>

Then you put your PHP code into a separate file: (I've called it data.php in the above example)

<?php
  require ('myConnect.php');     
  $id = $_GET['id'];
  $results = mysql_query("SELECT para FROM content WHERE  para_ID='$id'");   
  if( mysql_num_rows($results) > 0 )
  {
   $row = mysql_fetch_array( $results );
   echo $row['para'];
  }
?>

Adding Counter in shell script

Try this:

counter=0
while true; do
  if /home/hadoop/latest/bin/hadoop fs -ls /apps/hdtech/bds/quality-rt/dt=$DATE_YEST_FORMAT2 then
       echo "Files Present" | mailx -s "File Present"  -r [email protected] [email protected]
       break
  elif [[ "$counter" -gt 20 ]]; then
       echo "Counter limit reached, exit script."
       exit 1
  else
       let counter++
       echo "Sleeping for another half an hour" | mailx -s "Time to Sleep Now"  -r [email protected] [email protected]
       sleep 1800
  fi
done

Explanation

  • break - if files are present, it will break and allow the script to process the files.
  • [[ "$counter" -gt 20 ]] - if the counter variable is greater than 20, the script will exit.
  • let counter++ - increments the counter by 1 at each pass.

non static method cannot be referenced from a static context

Violating the Java naming conventions (variable names and method names start with lowercase, class names start with uppercase) is contributing to your confusion.

The variable Random is only "in scope" inside the main method. It's not accessible to any methods called by main. When you return from main, the variable disappears (it's part of the stack frame).

If you want all of the methods of your class to use the same Random instance, declare a member variable:

class MyObj {
  private final Random random = new Random();
  public void compTurn() {
    while (true) {
      int a = random.nextInt(10);
      if (possibles[a] == 1) 
        break;
    }
  }
}

Emulate a 403 error page

Use ModRewrite:

RewriteRule ^403.html$ - [F]

Just make sure you create a blank document called "403.html" in your www root or you'll get a 404 error instead of 403.

How can I convince IE to simply display application/json rather than offer to download it?

I found the answer.

You can configure IE8 to display application/json in the browser window by updating the registry. There's no need for an external tool. I haven't tested this broadly, but it works with IE8 on Vista.

To use this, remember, all the usual caveats about updating the registry apply. Stop IE. Then, cut and paste the following into a file, by the name of json-ie.reg.

Windows Registry Editor Version 5.00
;
; Tell IE to open JSON documents in the browser.  
; 25336920-03F9-11cf-8FD0-00AA00686F13 is the CLSID for the "Browse in place" .
;  

[HKEY_CLASSES_ROOT\MIME\Database\Content Type\application/json]
"CLSID"="{25336920-03F9-11cf-8FD0-00AA00686F13}"
"Encoding"=hex:08,00,00,00

[HKEY_CLASSES_ROOT\MIME\Database\Content Type\text/json]
"CLSID"="{25336920-03F9-11cf-8FD0-00AA00686F13}"
"Encoding"=hex:08,00,00,00

Then double-click the .reg file. Restart IE. The new behavior you get when tickling a URL that returns a doc with Content-Type: application/json or Content-Type: text/json is like this:

alt text

What it does, why it works:

The 25336920-03F9-11cf-8FD0-00AA00686F13 is the CLSID for the "Browse in place" action. Basically this registry entry is telling IE that for docs that have a mime type of application/json, just view it in place. This won't affect any application/json documents downloaded via <script> tags, or via XHR, and so on.

The CLSID and Encoding keys get the same values used for image/gif, image/jpeg, and text/html.

This hint came from this site, and from Microsoft's article Handling MIME Types in Internet Explorer .


In FF, you don't need an external add-on either. You can just use the view-source: pseudo-protocol. Enter a URL like this into the address bar:

view-source:http://myserver/MyUrl/That/emits/Application/json

This pseudo-protocol used to be supported in IE, also, until WinXP-sp2, when Microsoft disabled it for security reasons.

Use PPK file in Mac Terminal to connect to remote connection over SSH

Convert PPK to OpenSSh

OS X: Install Homebrew, then run

brew install putty

Place your keys in some directory, e.g. your home folder. Now convert the PPK keys to SSH keypairs:cache search

To generate the private key:

cd ~

puttygen id_dsa.ppk -O private-openssh -o id_dsa

and to generate the public key:

puttygen id_dsa.ppk -O public-openssh -o id_dsa.pub

Move these keys to ~/.ssh and make sure the permissions are set to private for your private key:

mkdir -p ~/.ssh
mv -i ~/id_dsa* ~/.ssh
chmod 600 ~/.ssh/id_dsa
chmod 666 ~/.ssh/id_dsa.pub

connect with ssh server

ssh -i ~/.ssh/id_dsa username@servername

Port Forwarding to connect mysql remote server

ssh -i ~/.ssh/id_dsa -L 9001:127.0.0.1:3306 username@serverName

Count the number of items in my array list

The only thing I would add to Mark Peters solution is that you don't need to iterate over the ArrayList - you should be able to use the addAll(Collection) method on the Set. You only need to iterate over the entire list to do the summations.

How can I enable MySQL's slow query log without restarting MySQL?

These work

SET GLOBAL LOG_SLOW_TIME = 1;
SET GLOBAL LOG_QUERIES_NOT_USING_INDEXES = ON;

Broken on my setup 5.1.42

SET GLOBAL LOG_SLOW_QUERIES = ON;
SET GLOBAL SLOW_QUERY_LOG = ON;
set @@global.log_slow_queries=1;

http://bugs.mysql.com/bug.php?id=32565

Looks like the best way to do this is set log_slow_time very high thus "turning off" the slow query log. Lower log_slow_time to enable it. Use the same trick (set to OFF) for log_queries_not_using_indexes.

Shrink to fit content in flexbox, or flex-basis: content workaround?

It turns out that it was shrinking and growing correctly, providing the desired behaviour all along; except that in all current browsers flexbox wasn't accounting for the vertical scrollbar! Which is why the content appears to be getting cut off.

You can see here, which is the original code I was using before I added the fixed widths, that it looks like the column isn't growing to accomodate the text:

http://jsfiddle.net/2w157dyL/1/

However if you make the content in that column wider, you'll see that it always cuts it off by the same amount, which is the width of the scrollbar.

So the fix is very, very simple - add enough right padding to account for the scrollbar:

http://jsfiddle.net/2w157dyL/2/

_x000D_
_x000D_
  main > section {_x000D_
    overflow-y: auto;_x000D_
    padding-right: 2em;_x000D_
  }
_x000D_
_x000D_
_x000D_

It was when I was trying some things suggested by Michael_B (specifically adding a padding buffer) that I discovered this, thanks so much!

Edit: I see that he also posted a fiddle which does the same thing - again, thanks so much for all your help

System.drawing namespace not found under console application

Add reference .dll file to project. Right, Click on Project reference folder --> click on Add Reference -->.Net tab you will find System.Drawing --> click on ok this will add a reference to System.Drawing

What are the "standard unambiguous date" formats for string-to-date conversion in R?

Converting the date without specifying the current format can bring this error to you easily.

Here is an example:

sdate <- "2015.10.10"

Convert without specifying the Format:

date <- as.Date(sdate4) # ==> This will generate the same error"""Error in charToDate(x): character string is not in a standard unambiguous format""".

Convert with specified Format:

date <- as.Date(sdate4, format = "%Y.%m.%d") # ==> Error Free Date Conversion.

Open Source Alternatives to Reflector?

2 options I know of.

  • CCI
  • Mono Cecil

These wont give you C# though.

Java: Convert a String (representing an IP) to InetAddress

From the documentation of InetAddress.getByName(String host):

The host name can either be a machine name, such as "java.sun.com", or a textual representation of its IP address. If a literal IP address is supplied, only the validity of the address format is checked.

So you can use it.

How to increase the gap between text and underlining in CSS

Getting into the details of the visual style of text-decoration:underline is pretty much futile, so you're going to have to go with some kind of hack the removes text-decoration:underline and replaces it with something else until a magical far-distant future version of CSS gives us more control.

This worked for me:

_x000D_
_x000D_
   a {_x000D_
    background-image: linear-gradient(_x000D_
        180deg, rgba(0,0,0,0),_x000D_
        rgba(0,0,0,0) 81%, _x000D_
        #222222 81.1%,_x000D_
        #222222 85%,_x000D_
        rgba(0,0,0,0) 85.1%,_x000D_
        rgba(0,0,0,0)_x000D_
    );_x000D_
    text-decoration: none;_x000D_
}
_x000D_
<a href="#">Lorem ipsum</a> dolor sit amet, <a href="#">consetetur sadipscing</a> elitr, sed diam nonumy eirmod tempor <a href="#">invidunt ut labore.</a>
_x000D_
_x000D_
_x000D_

  • Adjust the % values (81% and 85%) to change how far the line is from the text
  • Adjust the difference between the two % values to change the line thickness
  • adjust the color values (#222222) to change the underline color
  • works with multiple line inline elements
  • works with any background

Here's a version with all the proprietary properties for some backwards compatibility:

a {     
    /* This code generated from: http://colorzilla.com/gradient-editor/ */
    background: -moz-linear-gradient(top,  rgba(0,0,0,0) 0%, rgba(0,0,0,0) 81%, rgba(0,0,0,1) 81.1%, rgba(0,0,0,1) 85%, rgba(0,0,0,0) 85.1%, rgba(0,0,0,0) 100%); /* FF3.6+ */
    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,rgba(0,0,0,0)), color-stop(81%,rgba(0,0,0,0)), color-stop(81.1%,rgba(0,0,0,1)), color-stop(85%,rgba(0,0,0,1)), color-stop(85.1%,rgba(0,0,0,0)), color-stop(100%,rgba(0,0,0,0))); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(top,  rgba(0,0,0,0) 0%,rgba(0,0,0,0) 81%,rgba(0,0,0,1) 81.1%,rgba(0,0,0,1) 85%,rgba(0,0,0,0) 85.1%,rgba(0,0,0,0) 100%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(top,  rgba(0,0,0,0) 0%,rgba(0,0,0,0) 81%,rgba(0,0,0,1) 81.1%,rgba(0,0,0,1) 85%,rgba(0,0,0,0) 85.1%,rgba(0,0,0,0) 100%); /* Opera 11.10+ */
    background: -ms-linear-gradient(top,  rgba(0,0,0,0) 0%,rgba(0,0,0,0) 81%,rgba(0,0,0,1) 81.1%,rgba(0,0,0,1) 85%,rgba(0,0,0,0) 85.1%,rgba(0,0,0,0) 100%); /* IE10+ */
    background: linear-gradient(to bottom,  rgba(0,0,0,0) 0%,rgba(0,0,0,0) 81%,rgba(0,0,0,1) 81.1%,rgba(0,0,0,1) 85%,rgba(0,0,0,0) 85.1%,rgba(0,0,0,0) 100%); /* W3C */

    text-decoration: none;
}

Update: SASSY version

I made a scss mixin for this. If you don't use SASS, the regular version above still works great...

@mixin fake-underline($color: #666, $top: 84%, $bottom: 90%) {
    background-image: linear-gradient(
        180deg, rgba(0,0,0,0),
        rgba(0,0,0,0) $top,
        $color $top + 0.1%,
        $color $bottom,
        rgba(0,0,0,0) $bottom + 0.1%,
        rgba(0,0,0,0)
    );
    text-decoration: none;
}

then use it like so:

$blue = #0054a6;
a {
    color: $blue;
    @include fake-underline(lighten($blue,20%));
}
a.thick {
    color: $blue;
    @include fake-underline(lighten($blue,40%), 86%, 99%);
}

Update 2: Descenders Tip

If you have a solid background color, try adding a thin text-stroke or text-shadow in the same color as your background to make the descenders look nice.

Credit

This is simplified version of the technique I originally found at https://eager.io/app/smartunderline, but the article has since been taken down.

What is the difference between HTTP 1.1 and HTTP 2.0?

HTTP 2.0 is a binary protocol that multiplexes numerous streams going over a single (normally TLS-encrypted) TCP connection.

The contents of each stream are HTTP 1.1 requests and responses, just encoded and packed up differently. HTTP2 adds a number of features to manage the streams, but leaves old semantics untouched.

Special characters like @ and & in cURL POST data

cURL > 7.18.0 has an option --data-urlencode which solves this problem. Using this, I can simply send a POST request as

curl -d name=john --data-urlencode passwd=@31&3*J https://www.mysite.com

Eclipse keyboard shortcut to indent source code to the left?

Obviously this is only for Pydev, but I've worked out that you can get the very useful functions "Shift Right" and "Shift Left" (mapped by default to CTRL+ALT+. and CTRL+ALT+,) to become useful by changing their keybindings to "Pydev Editor Scope" from "Pydev View"

jQuery find parent form

see also jquery/js -- How do I select the parent form based on which submit button is clicked?

$('form#myform1').submit(function(e){
     e.preventDefault(); //Prevent the normal submission action
     var form = this;
     // ... Handle form submission
});

Http Post request with content type application/x-www-form-urlencoded not working in Spring

You have to tell Spring what input content-type is supported by your service. You can do this with the "consumes" Annotation Element that corresponds to your request's "Content-Type" header.

@RequestMapping(value = "/", method = RequestMethod.POST, consumes = {"application/x-www-form-urlencoded"})

It would be helpful if you posted your code.

Test if string begins with a string?

There are several ways to do this:

InStr

You can use the InStr build-in function to test if a String contains a substring. InStr will either return the index of the first match, or 0. So you can test if a String begins with a substring by doing the following:

If InStr(1, "Hello World", "Hello W") = 1 Then
    MsgBox "Yep, this string begins with Hello W!"
End If

If InStr returns 1, then the String ("Hello World"), begins with the substring ("Hello W").

Like

You can also use the like comparison operator along with some basic pattern matching:

If "Hello World" Like "Hello W*" Then
    MsgBox "Yep, this string begins with Hello W!"
End If

In this, we use an asterisk (*) to test if the String begins with our substring.

JavaScript single line 'if' statement - best syntax, this alternative?

You could use this format, which is commonly used in PHP:

(lemon) ? document.write("foo gave me a bar") : document.write("if condition is FALSE");

Subquery returned more than 1 value.This is not permitted when the subquery follows =,!=,<,<=,>,>= or when the subquery is used as an expression

You can use IN operator as below

select * from dbo.books where isbn IN
(select isbn from dbo.lending where lended_date between @fdate and @tdate)

Find a commit on GitHub given the commit hash

The ability to search commits has recently been added to GitHub.

To search for a hash, just enter at least the first 7 characters in the search box. Then on the results page, click the "Commits" tab to see matching commits (but only on the default branch, usually master), or the "Issues" tab to see pull requests containing the commit.

To be more explicit you can add the hash: prefix to the search, but it's not really necessary.

There is also a REST API (at the time of writing it is still in preview).

How set the android:gravity to TextView from Java side in Android

Solved this by doing a few things, first getting the height of my TextView and diving it by the text size to get the total amount of lines possible with the TextView.

int maxLines = (int) TextView.getHeight() / (int) TextView.getTextSize();

After you get this value you need to set your TextView maxLines to this new value.

TextView.setMaxLines(maxLines);

Set the Gravity to Bottom once the maximum amount of lines has been exceeded and it will scroll down automatically.

if (TextView.getLineCount() >= maxLines) {
    TextView.setGravity(Gravity.BOTTOM);
}

In order for this to work correctly, you must use append() to the TextView, If you setText() this will not work.

TextView.append("Your Text");

The benefit of this method is that this can be used dynamically regardless of the height of your TextView and the text size. If you decide to make modifications to your layout this code would still work.

Delete multiple rows by selecting checkboxes using PHP

Use array notation like name="checkbox[]" in your input element. This will give you $_POST['checkbox'] as array. In the query you can utilize it as

$sql = "DELETE FROM links WHERE link_id in ";
$sql.= "('".implode("','",array_values($_POST['checkbox']))."')";

Thats one single query to delete them all.

Note: You need to escape the values passed in $_POST['checkbox'] with mysql_real_escape_string or similar to prevent SQL Injection.

How should the ViewModel close the form?

public partial class MyWindow: Window
{
    public ApplicationSelection()
    {
      InitializeComponent();

      MyViewModel viewModel = new MyViewModel();

      DataContext = viewModel;

      viewModel.RequestClose += () => { Close(); };

    }
}

public class MyViewModel
{

  //...Your code...

  public event Action RequestClose;

  public virtual void Close()
  {
    if (RequestClose != null)
    {
      RequestClose();
    }
  }

  public void SomeFunction()
  {
     //...Do something...
     Close();
  }
}

Eclipse C++ : "Program "g++" not found in PATH"

WINDOWS 7

If there is anyone new reading this, make sure to simply try a clean install of mingw before any of this. It will save you sooooo much time if that is your problem.

I opened up wingw installer, selected every program for removal, apply changes (under installation tab, upper left corner), closed out, went back in and installed every file (in "Basic Setup" section) availible. after that eclipse worked fine using "MinGW GCC" toolchain when starting a new C++ project.

I hope this works for someone else. If not, I would do a reinstall of JDK (Java Developer's Kit) and ECLIPSE as well. I have a 64bit system but I could only get the 32bit versions of Eclipse and JDK to work together.

Using the && operator in an if statement

So to make your expression work, changing && for -a will do the trick.

It is correct like this:

 if [ -f $VAR1 ] && [ -f $VAR2 ] && [ -f $VAR3 ]
 then  ....

or like

 if [[ -f $VAR1 && -f $VAR2 && -f $VAR3 ]]
 then  ....

or even

 if [ -f $VAR1 -a -f $VAR2 -a -f $VAR3 ]
 then  ....

You can find further details in this question bash : Multiple Unary operators in if statement and some references given there like What is the difference between test, [ and [[ ?.