[2.9.x] We are testing upcoming JDK versions here

[mkurz]

I want to use this PR to test upcoming JDKs, so I will keep it open "forever" and just push to it from time to time.

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I set up a custom coursier index file that containts Java 21 (and soon newer) early access builds (because the default coursier index does not contain any):

• https://github.com/mkurz/jvm-index/blob/adoptium_temurin_eaps/index.json

(If you are interested it was done with this hacked commit so you can generate the json file yourself locally if you want)

You can access the index file yourself and use it if you want:

$ cs java --available --jvm-index https://github.com/mkurz/jvm-index/raw/adoptium_temurin_eaps/index.json
adoptium:1.21-ea26
adoptium:1.21-ea27
adoptium:1.21-ea28
adoptium:1.21-ea29
adoptium:1.21-ea30
adoptium:1.21-ea31
adoptium:1.21-ea32
adoptium:1.21-ea33
adoptium:1.21-ea34

Currently build 35 is the first release candidate for Java 21 LTS, see the announcement in the mailing list.

To make this work I needed to add the jvm-index argument to the coursier/setup-action workflow:

• Add support for --jvm-index coursier/setup-action#465

And of course we need to then integrate that argument into our repo workflows as well:

• playframework/.github@main...jvm-index

[mkurz]

All tests pass with JDK 21 🎉 ! IMHO it's safe to say we can officially support it for the 2.9 release. There will be another JDK21 release candidate (the last one) end of next week, I will then test as well, to make it 100% sure.
Ah, of course the only gotcha is the self signed certifacte stuff is not working in Java 21 anymore:

• Could not build with JDK 20 lightbend/ssl-config#367
• However a possible fix is there already: Jdk 20 compatibility lightbend/ssl-config#380

Not sure if for development purposes this is really relevant for the majority. Java 17 still works with it so not too bad.

[ihostage]

21.0.1 released yesterday 😉
https://github.com/adoptium/temurin21-binaries/releases/tag/jdk-21.0.1%2B12

[mkurz]

yeah, it's jdk 21 anyway 😉 Actually I want to set up Java 21 normally in our normal "check" workflow of course.