Java 7 - no more direct support by the Eclipse CI

[boaks]

Just to let all know:

Since yesterday, there is no more java 7 support for the CI Jenkins.
If java 7 would be required, that would need a special docker build image.
If using the compiler switch "-release" works, isn't known by me. In that past such similar approaches frequently failed for different reasons and therefore using a jdk 7 via the toolchain was the best option.
Anyway, I don't see, that I'm able to spend my time in overcome that. For Cf 4.0.0 the current plan is anyway to move to at least java 8. So, please try to check the nightly SNAPSHOT build, if that works for you and report, if you have some trouble.

[sbernard31]

Just to be clear for Californium 2.x and 3.x you will use -release right ?

[boaks]

yes.

[sbernard31]

At Leshan we use it for a while and nobody complain until now.
We also have a nightly build which builds with -release then execute tests with toolchains for minimal supported version + all Java LTS version above. E.g for Leshan 1.x, we execute tests with jdk toolchain 7, 8 , 11, 17, 21.

[boaks]

Not sure, if I remember it well, but java 8 introduces "covariant return types". Compiling code using java 8 API jars and just configure the compiler to generate java 7 classes failed then on that functions when executed with java 7.
I don't think, that java 7 is really still in use. And anyway, the next major release will not longer support java 7.

[sbernard31]

I think -release option aims to solve this kind of issue : https://bugs.openjdk.org/browse/JDK-8058150

[boaks]

One small downside:
Using --release doesn't work for toolchains targeting still java 8, because --release was introduced after java 8.
The build instructions need therefore also an update.

[sbernard31]

I missed that because I moved to Java 11 for building when I migrate to --release.
At the same time there is more more maven plugin which require java 11 as minimal version so maybe not so bad to move to java 11 for maven build.

[boaks]

Currently only "actinium" fails without real "toolchain" (I guess it's more about using oracle java 8 there, than just java 8.)

[boaks]

using

<maven.compiler.release></maven.compiler.release>

and the toolchain with oracle java 8 does it for actinium.

So, I guess removing the toolchain for californium and californium.tools works,
And I don't plan to keep "actinium" in Cf 4.0, so I also don't care too much about it.

[boaks]

Learning from my side:
It is less work to support only builds with newer jdks and only support to run it with older ones using the -release option ;-).

[rogierc]

Mule CoAP Connector requires java 8 support. No problem to drop java 7 support from there.