How do I pass default JVM args in a Gradle script while allowing variables to be expanded?

Question

I've got the following in my build.gradle.kts file:

plugins {
    kotlin("jvm") version "1.9.20"
    application
}

application {
    mainClass.set("MainKt")
    applicationDefaultJvmArgs = listOf("-Dlog_dir=MY_APP_HOME/log")
}

tasks.withType<CreateStartScripts>().configureEach {
    doLast {
        windowsScript.text = windowsScript.text.replace("MY_APP_HOME", "%APP_HOME%")
        unixScript.text = unixScript.text.replace("MY_APP_HOME", "\$APP_HOME")
    }
}

I've discovered that the unix shell script wraps my JVM args in single and double quotes.

DEFAULT_JVM_OPTS='"-Dlog_dir=$APP_HOME/log"'

Because of this, the variable $APP_HOME is not expanded and the log dir for my application is literally "$APP_HOME/log".

I cannot find any way to prevent this behavior. How can I get the variable to be expanded properly?

Answer 1

You can replace your placeholder "MY_APP_HOME" with the application home directory in a JVM argument using¹:

tasks.withType<CreateStartScripts>().configureEach {
    doLast {
        windowsScript.writeText(
            windowsScript.readText().replace("MY_APP_HOME", "%APP_HOME%")
        unixScript.writeText(
            unixScript.readText().replace("MY_APP_HOME", "'\$APP_HOME'")
        )
    }
}

I have used Kotlin's writeText and readText functions as the text operator on a File is only in Groovy, I believe.

---

¹Note this is guaranteed by an integration test in the Gradle project (written in Groovy): see GitHub.

The test code has two extra backslashes in its definition of the text to replace in the unix script: it writes "'\\\$APP_HOME'". Those extra backslashes are there because the test build file code that contains this is itself wrapped in triple quotes.