In a previous post we learned how to pass Java system properties from the command-line to a Java process defined in a Gradle build file. Because Grails 3 uses Gradle as the build tool we can apply the same mechanism in our Grails application. We need to reconfigure the run task. This task is of typeJavaExec and we can use the method systemProperties to assign the system properties we define on the command-line when we invoke the runtask.

We have a simple Grails 3 application with the following controller that tries to access the Java system property sample.message:

// File: grails-app/controllers/com/mrhaki/grails/SampleController.groovy
package com.mrhaki.grails

class SampleController {

    def index() {
        final String message =
            System.properties['sample.message'] ?: 'gr8'
        render "Grails is ${message}!"
    }
}

// File: build.gradle
...

[run, bootRun].each { runTask ->
    configure(runTask) {
        systemProperties System.properties
    }
}

...

Now we can invoke the run or bootRun tasks with Gradle:

Or we can execute the run-app command with the grails command: