How to customize JavaExec command line

Help/Discuss
1

Hello Everyone !

I have a project comprised of three java server apps. They need to run concurrently for me to use the application.

Gradle’s JavaExec waits for each java process to end (maybe that’s DefaultJavaExecAction:40) therefore only one JavaExec can run at a time.

I would like to customize JavaExec to build a different command line and instead of a myjava.exe -cp ... it would produce cmd /k start "myjava.exe -cp...". What would be the recommended approach to have such behavior ?

What we tried:

  • sneak in a change to commandLine but it’s read-only :wink:
  • use WorkerExecutor but it really doesn’t look right and seems to trigger multiple Gradle instances, eeeww
  • naively set executable to cmd /k start myjava.exe but javaexec seems to try to do a java -v first and is no longer to get its result :boom:
  • overriding JavaExec to leverage its classpath management…etc. work in progress but that proves to be trickier than I thought

Context:

  • Windows
  • Gradle 6.5.1
  • Java 8
  • can’t upload Gradle scan - company policy, sorry

Any pointer to a clean solution would be greatly appreciated.

Thank-you !

2

The three app are defined in distinct subprojects and --parallel should be able to have them all run concurrently but that would be nice to not have to use a flag every time (and enabling it by default is not currently an acceptable option in our build).

3

Ended up doing something like that below but it doesn’t work with Gradle 6.6 (worked with 6.5.1). Any idea why it doesn’t work with 6.6 ? looks like commandLine only contains the executable now.

@CompileStatic
class ServerJavaExec extends JavaExec {

    private final Property<ExecResult> serverJavaExecResult;

    def serverName

    ServerJavaExec() {
         super()
         serverJavaExecResult = objectFactory.property(ExecResult.class);
    }

    @Override
    @TaskAction
    public void exec() {
        // drop the first item in commandLine, it is the executable (java.exe)
        def javaCommandArgsLine = commandLine.drop(1).join(' ')
        def javaCommand = "cmd /k start \"$serverName\" \"$executable\" $javaCommandArgsLine"

        getLogger().info "Executing $javaCommand ..."
        // >> Here I execute javaCommand, it eventually goes to process builder <<

        // immediately return a success result
        serverJavaExecResult.set([
            exitValue: 0,
            assertNormalExitValue: this,
            rethrowFailure: this
        ] as ExecResult);
    }

    @Override
    public Provider<ExecResult> getExecutionResult() {
       return serverJavaExecResult;
    }
}