Jdk 21 news scenario for some JEPs

[jedla97]

Hi, this PR adding showcase of some new features from JDK18-21.

The CI only adding JDK21 to jvm runs, as there is not ubi-quarkus-mandrel-builder-image available for JDK21.

Adding of -Dnet.bytebuddy.experimental=true is because bytebuddy is transitive dependency of hibernate and probably latest Quarkus don't have updated hibernate version which support latest bytebuddy (maybe even bytebuddy don't have version which goes from experimental to supported as latest version was released before JDK21)

[rsvoboda]

there is not ubi-quarkus-mandrel-builder-image available for JDK21

I asked about it and there should be one within a month more or less. It's based on Temurin which is not in final version.
We may need some fixes on Quarkus side too.

[rsvoboda]

Other things to check (or to tell me that they were checked or make no sense to you to be checked):

Sequenced collections with Hibernate, Sequenced collections with rest apis through json binding ...

String templates and QUTE (https://quarkus.io/guides/qute-reference)

Unnamed classes and instance main methods with

• Quarkus command line apps (https://quarkus.io/guides/command-mode-reference)
• Customized boot of Quarkus application (https://quarkus.io/guides/lifecycle#the-main-method)

Vector API introduces new classes (https://docs.oracle.com/en/java/javase/21/docs/api/jdk.incubator.vector/jdk/incubator/vector/package-summary.html) maybe worth checking if they can be easily used in rest endpoints and in JPA.

[jedla97]

@rsvoboda Generally I create only showcase of new features which are ready (not preview or incubator) at least I take it we should watch them but they can never make it from preview or be discontinued.

For what I just try but not implement in this PR:

• String templates (preview)
• Unnamed Patterns and Variables (Preview) with enhanced switch case
• Try virtual threads when main source was this
• Sequenced Collections but my ideas just doesn't make most of the sense as I tried just basic new methods

But thanks for suggesting using the Sequenced Collections with hibernate I just get some idea which I'll try.

But if you want I can create some showcases for previews? I have some in mind.

For Unnamed classes and instance main methods with I don't think we need them here but just tried if it work would wort a shot.

[rsvoboda]

Generally I create only showcase of new features which are ready (not preview or incubator)

OK, makes sense

But if you want I can create some showcases for previews? I have some in mind.

+1 for it, people will try preview stuff

Unnamed classes and instance main methods

it's ok to just check locally, should work, but Quarkus does some bytecode magic, so worth checking

[rsvoboda]

@jedla97 just fyi, I checked simplified main and Quarkus has issues with that - quarkusio/quarkus#36154

[jedla97]

@rsvoboda I added the sequenced collection with hibernate. Unified the posgres version. At the moment I can't add preview because test framework not passing the --enable-preview when execute the jar so there will be need to update framework after I'll add it there.

Thanks for the testing the simplified main. +1

[michalvavrik]

It don't need to be in this PR as it is not specific for 21, but I can see you are using records, so it'd be nice if you found scenario that catch template records as I don't believe we are testing it otherwise and native methods are ugly https://quarkus.io/guides/qute-reference#template-records. Just if you can.

[michalvavrik]

Sorry, wrong, button, I wanted to write comment :/