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 type JavaExec and we can use the method systemProperties to assign the system properties we define on the command-line when we invoke the run task.

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}!"
    }
}

Next we configure the run and bootRun tasks and use System.properties with the Java system properties from the command-line as argument for the systemProperties method:

// File: build.gradle
...

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

...

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

$ gradle -Dsample.message=cool run

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

grails> run-app -Dsample.message=cool

Written with Grails 3.0.7.

Original article