Specifying Gradle version and Java toolchain version isn't enough

Help/Discuss
1

I just encountered a curious issue… maybe not a bug, but it caught me off guard. I figured that using a build.gradle file with:

java {
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(17))
    }
}

and the gradle wrapper to specify Gradle 7.2, that my build should work consistently on different machines. It does not.
It is still very much dependent on what version of the JVM is running the gradle daemon. Otherwise you can get errors like this:

FAILURE: Build failed with an exception.

* What went wrong:

java.lang.UnsupportedClassVersionError: org/openjfx/gradle/JavaFXPlugin has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

> org/openjfx/gradle/JavaFXPlugin has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0

Is there a standard way of telling Gradle that the daemon itself must be running with a specific minimum JVM version? Something that can be put in the project build script so it doesn’t rely on setting up the machine just right before hand?

Since the error is triggered by applying a plugin, I have come up with this early check. Is there a better way? Is there a way to get Gradle to launch a daemon running on the correct JVM version so it all “just works” ?

build script {
  if (!JavaVersion.current().java11Compatible) {
    throw new GradleException("Gradle daemon must be running on Java 11 or greater.")
  }
}
plugins {
  id 'application'
  id 'org.openjfx.javafxplugin' version '0.0.8'
}
2

I had a similar problem, running tests of java project with launcherJava set to 11.

javaLauncher = javaToolchains.launcherFor {
        languageVersion = JavaLanguageVersion.of(14)
    }

I got an error pretty similar error related to an unsupported class version

This is my config

  • Gradle 7.3
  • java 17

the project has this structure:
project (java 17)

  • module (tests on java 11)
  • other Java 17 modules…

The same problem does not occur if I set the global java version to 11 and run the tests. So it seems that the toolchains do not insulate everything.

Any thoughts on this?