How to invoke a method in Custom Gradle Task?

Question

I am trying to build a custom Gradle Task to perform some app maintenance operations. I would like to pass argument(s) to the task to control operations. To illustrate my dilemma, consider to following two trivial custom task classes:

// Custom task with no arguments
public class HelloClassA extends DefaultTask {
    @TaskAction
    public void printHello()
    {
        println "Hello, World!"
    }
}

// Custom task with one argument
public class HelloClassB extends DefaultTask {
    @TaskAction
    public void printMsg(String msg)
    {
        println msg
    }
}

They are identical except that "A" prints a hard-coded string while "B" accepts a string as an argument.

Class A is used in the following task:

task helloA(type:HelloClassA) { }

and is invoked by, e.g.,

gradlew.bat helloA

It works fine and prints "Hello, World!" to the Build window. However, I can't figure out the syntax is for a task to invoke Class B.

How do I do that? (or am I just way off base trying to do it this way?)

Some rather Strange Things I've noticed...

The name of the method in the classes (e.g., "printHello") seems to be irrelevant: any reasonable name produces identical output (?).
When invoking by gradlew.bat, any unambiguous substring of the task name works the same, e.g., "GRADLEW helloA" or "GRADLEW hell". I guess this is just GRADLE trying to be helpful (?).

It seems like you're asking ["How to pass an argument to a Gradle task?"](https://stackoverflow.com/a/26510706/1005481) The short answer is: You cannot do it using method arguments, you must use project properties. — barfuin, Jun 30 '21 at 15:23

score 1 · Answer 1 · answered Jun 30 '21 at 15:38

You can't directly pass it as an argument to the method. But, if you wish there is a way using @Input annotation.

Following is the example for you use case:

abstract class HelloClassB extends DefaultTask {
    @Input
    abstract Property<String> getMsg()//this is an abstract method to get values

    @TaskAction
    def printMsg() {
        println msg.get() // here we get the value set from task.register
    }
}

// printB is the task name 
tasks.register('printB',HelloClassB) {
    msg = 'Hello B' // here we set the Input value
}

Now in your terminal run: gradlew -q printB

If you want to read more about this then please have a look here: https://docs.gradle.org/current/userguide/custom_tasks.html

DontPanic · Accepted Answer · 2021-07-15T16:03:39.430

You can pass an argument(s) directly to a method without using properties. Here's how:

apply plugin: 'com.android.application'

import javax.inject.Inject

abstract class CustomTask extends DefaultTask {
    @Inject
    CustomTask(String message,int number) {
        println "Processing \""+message+"\", "+number    // process args
    }
}

Create task 'mytask' as follows in the android section appending the arguments (which must agree in count and format with the task definitions):

tasks.register( 'mytask', CustomTask, 'Hello, World!', 123 )

Execute 'mytask' by

gradlew.bat mytask

which produces the output

Processing "Hello, World!", 123

This is actually a constructor parameter, not a method argument. — barfuin, Mar 07 '22 at 20:23

How to invoke a method in Custom Gradle Task?

2 Answers2