run main method using gradle "run" task

Question

I want to run my main method via gradle task

This is how I run via the cmd:

java -cp RTMonitor.jar com.bla.MainRunner first_arg

how should it be written in gradle?

run {
    args += ['java -cp RTMonitor.jar com.bla.MainRunner first_arg']
}

Update

I have tried

task myRun(type: JavaExec) {
    classpath configurations.main
    main = "com.bla.runners.StatsLogGenerator"
    args "arg1", "arg2"
}

and I got:

Error:(71, 0) Could not find property 'main' on configuration container.

the I have tried:
    task myRun(type: JavaExec) {
        classpath "configurations.main"
        main = "com.bla.runners.StatsLogGenerator"
        args "arg1", "arg2"
    }

and i got an error:

FAILURE: Build failed with an exception.
17:49:21.855 [ERROR] [org.gradle.BuildExceptionReporter] 
17:49:21.856 [ERROR] [org.gradle.BuildExceptionReporter] * What went wrong:
17:49:21.856 [ERROR] [org.gradle.BuildExceptionReporter] Execution failed for task ':myRun'.
17:49:21.856 [ERROR] [org.gradle.BuildExceptionReporter] > Process 'command '/Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home/bin/java'' finished with non-zero exit value 1
17:49:21.864 [ERROR] [org.gradle.BuildExceptionReporter] 
17:49:21.865 [ERROR] [org.gradle.BuildExceptionReporter] * Exception is:
17:49:21.866 [ERROR] [org.gradle.BuildExceptionReporter] org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':myRun'.
17:49:21.867 [ERROR] [org.gradle.BuildExceptionReporter]    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:69)

17:49:21.882 [ERROR] [org.gradle.BuildExceptionReporter]    at org.gradle.process.internal.DefaultExecHandle$ExecResultImpl.assertNormalExitValue(DefaultExecHandle.java:361)
17:49:21.882 [ERROR] [org.gradle.BuildExceptionReporter]    at org.gradle.process.internal.DefaultJavaExecAction.execute(DefaultJavaExecAction.java:31)

but when I run via Intellij, every thig works OK

Bemuse

Answer 1

The easiest is probably to use application plugin. Add apply plugin: 'application' to your build.gradle and set mainClassName = com.bla.MainRunner . To add arguments to your main class modify the run task and edit the args property

run {
  args += 'first_arg'
}

Classpath is taken automatically from main sourceSet, if you want different one, you can edit classpath property of the run task.

If you need more customization, you can define your own task of type JavaExec like this

task myRun(type: JavaExec) {
  classpath sourceSets.main.runtimeClasspath
  main = "com.bla.MainRunner"
  args "arg1", "arg2"
}

Romaic

and what if I have two main methods, and I want to define a different task for each? mainClassName is assign in the global scope? – Bemuse

then you will be likely better of defining your own task of type JavaExec – Romaic

where is the doc to see which properties each task type has? – Bemuse

In the DSL Reference guide. For JavaExec here gradle.org/docs/current/dsl/org.gradle.api.tasks.JavaExec.html – Romaic

Error:(71, 0) Could not find property 'main' on configuration container. – Bemuse

sorry, my error, classpath should be something like sourceSets.main.runtimeClasspath – Romaic

Answer 2

task run(type: JavaExec) {
  group = 'Run' // <-- change the name as per your need
  description = 'Small description what this run will do'

  classpath sourceSets.main.runtimeClasspath // <-- Don't change this
  main = "com.mypackage.myclassNameContaingMainMethod"
  args "arg1", "arg2"
}

This is a independent registered task and can also have group and description and other properties of task.

Unceasing

Answer 3

In gradle 6.4+, the mainClassName property exposed by the application plugin has been renamed to mainClass. So the configuration would look something like below(in Kotlin DSL):

plugins {
    application
}

application {
    mainClass.set("com.bla.MainRunner")
}

tasks.run<JavaExec> {
    args(listOf("first_arg"))
}

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