Support JDK9 methods using MR-JAR

[FroMage]

WDYT @manovotn ? I'm not too sure how to test this though. I have to check how other projects do it in the CI.

[manovotn]

I'm not too sure how to test this though.

Hmm, not sure either. We would need some special settings for surefire plugin that only adds certain test sources with JDK 9+?

[FroMage]

@manovotn I've updated the way I do the MR to the first option recommended on https://maven.apache.org/plugins/maven-compiler-plugin/multirelease.html which means we have two virtual modules:

• core-java8 (the base)
• core-java9 (the MR for 9)

and core just assembles the two into an MR jar.

It's more standard build for Maven I guess, but it has two drawbacks:

• Eclipse can't load the modules properly because it doesn't see that the core module has classes, so you need to add the core-java8/9 projects to its build path.
• Dependencies from core-java8 need to be duplicated in core because that's the pom that will be used.

I added tests for the new methods too.

[FroMage]

Updated it again with the structure supported by smallrye-parent, that's much cleaner.

[manovotn]

I am probably missing something but why do you need empty files such as core/build-release-8 or tests/build-release-8?

Otherwise looks pretty good.

[FroMage]

I think this PR's CI is toast, lemme reopen one.

[FroMage]

Same CI issue so let's keep this one open.

[FroMage]

Finally, CI rules are fixed.

[dmlloyd]

I am probably missing something but why do you need empty files such as core/build-release-8 or tests/build-release-8?

Otherwise looks pretty good.

Have a look at the docs here: https://github.com/smallrye/smallrye-parent/blob/master/README.adoc