This commit upgrades the CI pipeline with the following:
* replace JDK16 with JDK17 as build variant
* upgrade all JDK versions
* replace docker-image with registry-image resource for CI image
This commit adds a new JDK 18 variant to the CI build image and
configures a JDK18 build (sources compiled with JDK17, tests compiled
and run with JDK18) to the CI pipeline.
Closes gh-27607
This commit introduces a new `spring-framework-6.0.x` CI pipeline with
JDK 17 baseline.
Note that Kotlin still uses a JDK11 baseline for now, this will be
addressed in gh-27413.
Closes gh-27409
Prior to this commit, the Spring Framework build would rely on
setting a custom Java HOME for building all sources and tests
with that JDK.
This approach is not flexible enough, since we would be testing
the source compatibility against a recent JDK, but not a common
case experienced by the community: compiling and running
application code with a recent JDK and the official, JDK8-based
Framework artifacts.
This method is also limiting our choice of JDKs to the ones
currently supported by Gradle itself.
This commit introduces the support of Gradle JVM Toolchains in
the Spring Framework build.
We can now select a specific JDK for compiling the main
SourceSets (Java, Groovy and Kotlin) and another one for
compiling and running the test SourceSets:
`./gradlew check -PmainToolChain=8 -PtestToolchain=15`
Gradle will automatically find the JDKs present on the host or
download one automcatically. You can find out about the ones
installed on your host using:
`./gradlew -q javaToolchains`
Finally, this commit also refactors the CI infrastructure to:
* only have a single CI image (with all the supported JDKs)
* use this new feature to compile with JDK8 but test it
against JDK11 and JDK15.
Closes gh-25787
