Add Java Development Environment 21

[opajonk]

Some tools (specifically PlantUML in this case) require a JDK, hence we install it. Bazel's rules_java requires that JAVA_HOME is set appropriately, so we do that as well.

[AlexanderLanin]

Does it make sense to install the jdk? As bazel will do it redundantly anyway

[AlexanderLanin]

And if so, we need to discuss the exact version. Compare https://github.com/eclipse-score/dash-license-scan/blob/607e8f1879d9856e812746aa1a190bb0b598187a/src/dash_license_scan/jar.py#L31

[opajonk]

Does it make sense to install the jdk? As bazel will do it redundantly anyway

Bazel actually used the JAVA_HOME environment variable. And then it complained, that I installed only a JRE :-)

[opajonk]

And if so, we need to discuss the exact version. Compare https://github.com/eclipse-score/dash-license-scan/blob/607e8f1879d9856e812746aa1a190bb0b598187a/src/dash_license_scan/jar.py#L31

No need to discuss, I can change it to 21.

[AlexanderLanin]

It's still jdk vs jre. And I still wonder why it's needed. Bazel will download it's own version anyway... which is 17 by the way 😆

https://github.com/eclipse-score/reference_integration/blob/af717c2ea97aef3f5363b652ce36672b78dbaf76/.bazelrc#L58-L61

[opajonk]

It's still jdk vs jre.

Well now I am installing the JDK. Bazel was complaining that the Java in JAVA_HOME was a JRE :-) So, I think it is using it after all?

[AlexanderLanin]

As discussed we want to move tooling from bazel to devcontainer. So let's include java.

Optimizing jdk to jre is a separate topic.