Choosing the correct JRE version in Gradle with Eclipse

Question

I\'m using Gradle with the Eclipse plugin to generate project files for my project, but I can\'t get it to put the correct JRE version in .classpath. I can

Answer 1

I found that the proposed solution causes duplicate entries on subsequent 'gradle eclipse' executions. Borrowing some code from Specifiy JRE Container with gradle eclipse plugin, I came up with the following which seems to work:

project.afterEvaluate {
  // use jre lib matching version used by project, not the workspace default
  if (project.sourceCompatibility != null) {
    def target = project.sourceCompatibility.toString()
    def containerPrefix = "org.eclipse.jdt.launching.JRE_CONTAINER"
    def containerSuffix
    if (target =~ /1.[4-5]/) {
      containerSuffix = '/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/J2SE-' + target
    } else if (target =~ /1.[6-8]/) {
      containerSuffix = '/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-' + target
    }
    if (containerSuffix != null) {
      project.eclipse.classpath {
        containers.removeAll { it.startsWith(containerPrefix) }
        containers.add(containerPrefix + containerSuffix)
      }
    }
  }
}

Answer 2

I've ended up solving this in a slightly more manual way than I wanted - but at least it works.

In order to separate the settings from the implementation, each developer has a gradle.properties file which is not checked into version control. This file contains the following information (on my workstation):

javaVersion=1.6
javaPath=C:/Program/Java/jdk1.6.0_45
jdkName=jdk1.6.0_45

In the build script, i then do the following to get all the configuration correct:

// Set sourceCompatibility
if (project.hasProperty('javaVersion')) {
    project.sourceCompatibility = project.javaVersion
}

// Set bootClasspath - but wait until after evaluation, to have all tasks defined
project.afterEvaluate {
    if (project.hasProperty('javaPath')) {
        project.tasks.withType(AbstractCompile, {
            it.options.bootClasspath = "${project.javaPath}/jre/lib/rt.jar"
        })
    }
}

// Configure Eclipse .classpath
project.eclipse.classpath.file.whenMerged { Classpath cp ->
    if (project.hasProperty('jdkName') {
        cp.entries.findAll { it.path.contains('JRE_CONTAINER') }.each {
            it.path += "/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/$project.jdkName"
        }
    }
}

So far I've used it in a couple of projects and it's worked, so I guess it's at least quite portable - but it might be necessary to make slight modifications to make it work for others.