SpringBoot Gradle AOT processing tasks do not use project's Java toolchain

The current processAot task does not utilize the gradle toolchain, and it will fail if the Java environment version is lower than the toolchain language version. In my project settings, I have defined the Java language version as 21 using the following configuration:

java {
    toolchain {
        languageVersion.set(JavaLanguageVersion.of(21))
    }
}

However, my Java environment is using Java 17. When I run gradle build, it fails with the following error:

Task :processAot FAILED
Exception in thread "main" java.lang.UnsupportedClassVersionError: com/oldshensheep/Main has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 61.0
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1017)
    at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
    at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
    at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:525)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:375)
    at org.springframework.boot.SpringApplicationAotProcessor.main(SpringApplicationAotProcessor.java:70)

Execution failed for task ':processAot'.
> Process 'command 'E:\apps\scoop\apps\temurin-lts-jdk\current\bin\java.exe'' finished with non-zero exit value 1

I've found similar issues, but it is not the case:

https://github.com/spring-io/initializr/issues/1187 https://github.com/spring-projects/spring-boot/issues/33365

Comment From: wilkinsona

Thanks for the report. We do this already for bootRun and the new bootTestRun task but overlooked it when introducing processAot and processTestAot.

Until a fix is released, you can work around the problem by configuring the toolchain in your build. Something like this:

tasks.withType(JavaExec).configureEach {
    javaLauncher.set(javaToolchains.launcherFor(java.toolchain))
}

Comment From: oldshensheep

@wilkinsona It's working, but I need to replace JavaExec with JavaExec::class.

Comment From: larsgrefer

I used this similar workaround:

https://github.com/joinfaces/joinfaces/blob/91aac91b7cd1de63e25fae1f477a6eb6604009b4/test-projects/build.gradle#L37-L42