Gradle JavaExec Task Type

External

• https://docs.gradle.org/current/dsl/org.gradle.api.tasks.JavaExec.html
• https://docs.gradle.org/current/javadoc/org/gradle/api/tasks/JavaExec.html
• https://www.baeldung.com/gradle-run-java-main

Internal

• Java Plugin
• Gradle Tasks

Overview

Executes a Java application as a child process. To get details on the actual java command line, execute Gradle with -i command line option. While the execution task name can be arbitrary, "run" is usually a good choice.

task someTask(type: JavaExec) {
    classpath = configurations.runtimeClasspath
    main = 'myPackage.MyMainClass'
    args = ['something', 'somethingelse']
    jvmArgs = ['-Xmx12G', '-Xms1G']
    environment "LD_LIBRARY_PATH", "/usr/local/lib"
    systemProperties = [ "some.prop": "some.value", "some.other.prop": "some.other.value" ]
}

Debugging Code Run with JavaExec

task someTask(type: JavaExec) {
    classpath = configurations.runtimeClasspath
    main = 'myPackage.MyMainClass'
    args = ['something', 'somethingelse']
    jvmArgs = ['-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=5005']
}

The above configuration will start the JVM executing 'myPackage.MyMainClass' in debug mode and suspend waiting for a connection on 5005. For a process model, see

Gradle Process Model | Daemon | JavaExec

Configuration

classpath

TODO

classpath = sourceSets.main.runtimeClasspath

classpath = configurations.runtimeClasspath

classpath = configurations.compileClasspath

main

The main class. Must be available on classpath.

main = 'playground.javaExec.Main'

args

"args" can be provided as a single string, but in this case, even if individual tokens are separated by space, the main() method will get just one single string as argument:

args 'A B C'

This will be passed to the Java main() method as args[0]:

arguments:
  args[0]: X Y Z

To provide individual tokens, use this syntax:

args = ['A', 'B', 'C']

The list elements will be passed to the Java main() method as individual arguments:

arguments:
  args[0]: A
  args[1]: B
  args[2]: C

jvmArgs

jvmArgs = ['-Xmx12g']

environment

Specifies a single environment variable, as a key value pair separated by comma. Multiple variable can be specified that way:

environment "SOME_ENV_VAR", "some value"
environment "SOME_OTHER_ENV_VAR", "some other value"

systemProperties

A Groovy map.

systemProperties = [ "some.prop": "some.value", "some.other.prop": "some.other.value" ]

standardOutput

task someTask(type: JavaExec) {
  ...
  standardOutput = System.out
  ...
}

errorOutput

task someTask(type: JavaExec) {
  ...
  errorOutput = System.err
  ...
}