spring-boot-grade-toolchain

Testbed for reproductions of spring boot interactions with the new Gradle toolchain support.

Running Gradle with Java 8, using the Gradle toolchain to apply different Java versions.

BootRun doesn't use toolchain

By default, bootRun will use the toolchain running the Gradle build.

So if we run Gradle with Java 8 but select to use a newer toolchain:

java {
	toolchain {
		languageVersion = JavaLanguageVersion.of(15)
	}
}

bootRun will fail unless/until we add the following:

bootRun {
	javaLauncher = javaToolchains.launcherFor {
		languageVersion = JavaLanguageVersion.of(15)
	}
}

This seems by design from Gradle that it will:

Setup all compile, test and javadoc tasks to use the defined toolchain which may be different than the one Gradle itself uses (https://docs.gradle.org/current/userguide/toolchains.html)

Without reference to JavaExec, which I guess are intended to be set manually.

In any case, with this block commented-out, we get an error on bootRun related to trying to run the Java 15-compiled code with Gradle's Java 8.

So for Spring Boot's bootRun at least, if it is not the intent of Gradle to apply this automatically to JavaExec tasks it might be nice to have it applied by default to BootRun ones at least.

BootRun warning

During bootRun (with setup as committed here) a warning is emitted:

OpenJDK 64-Bit Server VM warning: Options -Xverify:none and -noverify were deprecated in JDK 13 and will likely be removed in a future release.

This appears to be a regression related to this fix, which implicitly assumes (in BootRun#isJava13OrLater) that the JDK running the build is the same as running the application in bootRun, which is not true in this setup.

https://github.com/scope-demo/spring-boot/commit/af223c21c512ed1a67e23672905a2986ea23701b