[gradle] How to pass arguments from command line to gradle

I'm trying to pass an argument from command line to a java class. I followed this post: http://gradle.1045684.n5.nabble.com/Gradle-application-plugin-question-td5539555.html but the code does not work for me (perhaps it is not meant for JavaExec?). Here is what I tried:

task listTests(type:JavaExec){
    main = "util.TestGroupScanner"
    classpath = sourceSets.util.runtimeClasspath
    // this works...
    args 'demo'
    /*
    // this does not work!
    if (project.hasProperty("group")){
        args group
    }
    */
}

The output from the above hard coded args value is:

C:\ws\svn\sqe\sandbox\selenium2forbg\testgradle>g listTests
:compileUtilJava UP-TO-DATE
:processUtilResources UP-TO-DATE
:utilClasses UP-TO-DATE
:listTests
Received argument: demo

BUILD SUCCESSFUL

Total time: 13.422 secs

However, once I change the code to use the hasProperty section and pass "demo" as an argument on the command line, I get a NullPointerException:

C:\ws\svn\sqe\sandbox\selenium2forbg\testgradle>g listTests -Pgroup=demo -s

FAILURE: Build failed with an exception.

* Where:
Build file 'C:\ws\svn\sqe\sandbox\selenium2forbg\testgradle\build.gradle' line:25

* What went wrong:
A problem occurred evaluating root project 'testgradle'.
> java.lang.NullPointerException (no error message)

* Try:
Run with --info or --debug option to get more log output.

* Exception is:
org.gradle.api.GradleScriptException: A problem occurred evaluating root project
 'testgradle'.
    at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:54)
    at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl.apply(DefaultScriptPluginFactory.java:127)
    at org.gradle.configuration.BuildScriptProcessor.evaluate(BuildScriptProcessor.java:38) 

There is a simple test project available at http://gradle.1045684.n5.nabble.com/file/n5709919/testgradle.zip that illustrates the problem.

This is using Gradle 1.0-rc-3. The NullPointer is from this line of code:

args group 

I added the following assignment before the task definition, but it didn't change the outcome:

group = hasProperty('group') ? group : 'nosuchgroup' 

Any pointers on how to pass command line arguments to gradle appreciated.

My program with two arguments, args[0] and args[1]:

public static void main(String[] args) throws Exception {
    System.out.println(args);
    String host = args[0];
    System.out.println(host);
    int port = Integer.parseInt(args[1]);

my build.gradle

run {
    if ( project.hasProperty("appArgsWhatEverIWant") ) {
        args Eval.me(appArgsWhatEverIWant)
    }
}

my terminal prompt:

gradle run  -PappArgsWhatEverIWant="['localhost','8080']"

As of Gradle 4.9 Application plugin understands --args option, so passing the arguments is as simple as:

build.gradle

plugins {
    id 'application'
}

mainClassName = "my.App"

src/main/java/my/App.java

public class App {
    public static void main(String[] args) {
        System.out.println(args);
    }
}

bash

./gradlew run --args='This string will be passed into my.App#main arguments'

or in Windows, use double quotes:

gradlew run --args="This string will be passed into my.App#main arguments"

It's possible to utilize custom command line options in Gradle to end up with something like:

./gradlew printPet --pet="puppies!"

However, custom command line options in Gradle are an incubating feature.

Java solution

To end up with something like this follow the instructions here:

import org.gradle.api.tasks.options.Option;

public class PrintPet extends DefaultTask {
    private String pet;

    @Option(option = "pet", description = "Name of the cute pet you would like to print out!")
    public void setPet(String pet) {
        this.pet = pet;
    }

    @Input
    public String getPet() {
        return pet;
    }

    @TaskAction
    public void print() {
        getLogger().quiet("'{}' are awesome!", pet);
    }
}

Then register it:

task printPet(type: PrintPet)

Now you can do:

./gradlew printPet --pet="puppies"

output:

Puppies! are awesome!

Kotlin solution

open class PrintPet : DefaultTask() {

    @Suppress("UnstableApiUsage")
    @set:Option(option = "pet", description = "The cute pet you would like to print out")
    @get:Input
    var pet: String = ""

    @TaskAction
    fun print() {    
        println("$pet are awesome!")
    }
}

then register the task with:

tasks.register<PrintPet>("printPet")

I have written a piece of code that puts the command line arguments in the format that gradle expects.

// this method creates a command line arguments
def setCommandLineArguments(commandLineArgs) {
    // remove spaces 
    def arguments = commandLineArgs.tokenize()

            // create a string that can be used by Eval 
            def cla = "["
            // go through the list to get each argument
            arguments.each {
                    cla += "'" + "${it}" + "',"
            }

    // remove last "," add "]" and set the args 
    return cla.substring(0, cla.lastIndexOf(',')) + "]"
}

my task looks like this:

task runProgram(type: JavaExec) {
    if ( project.hasProperty("commandLineArgs") ) {
            args Eval.me( setCommandLineArguments(commandLineArgs) )
    }
}

To pass the arguments from the command line you run this:

gradle runProgram -PcommandLineArgs="arg1 arg2 arg3 arg4"    

If you need to check and set one argument, your build.gradle file would be like this:

....

def coverageThreshold = 0.15

if (project.hasProperty('threshold')) {
    coverageThreshold = project.property('threshold').toString().toBigDecimal()
}

//print the value of variable
println("Coverage Threshold: $coverageThreshold")
...

And the Sample command in windows:

gradlew clean test -Pthreshold=0.25

pass a url from command line keep your url in app gradle file as follows resValue "string", "url", CommonUrl

and give a parameter in gradle.properties files as follows CommonUrl="put your url here or may be empty"

and pass a command to from command line as follows gradle assembleRelease -Pcommanurl=put your URL here

Building on Peter N's answer, this is an example of how to add (optional) user-specified arguments to pass to Java main for a JavaExec task (since you can't set the 'args' property manually for the reason he cites.)

Add this to the task:

task(runProgram, type: JavaExec) {

  [...]

  if (project.hasProperty('myargs')) {
      args(myargs.split(','))
  }

... and run at the command line like this

% ./gradlew runProgram '-Pmyargs=-x,7,--no-kidding,/Users/rogers/tests/file.txt'

There's a great example here:

https://kb.novaordis.com/index.php/Gradle_Pass_Configuration_on_Command_Line

Which details that you can pass parameters and then provide a default in an ext variable like so:

gradle -Dmy_app.color=blue

and then reference in Gradle as:

ext {
   color = System.getProperty("my_app.color", "red");
}

And then anywhere in your build script you can reference it as course anywhere you can reference it as project.ext.color

More tips here: https://kb.novaordis.com/index.php/Gradle_Variables_and_Properties