[Feature Request]: Support Java 21

[deathstarjanitor]

What would you like to happen?

Java 21 is expected to release in September, 2023.
https://www.java.com/releases/matrix/

Beam should support building Java pipelines using the Java 21 SDK.
Beam should also support running on the Java 21 runtime.

Issue Priority

Priority: 2 (default / most feature requests should be filed as P2)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner

[Abacn]

Currently, testing on Java11 and 17 are configured with "giant" gradle property compileAndRunTestsWithJava11 and compileAndRunTestsWithJava17 . As we add one more version, we should just have a testJavaVersion separate from beamJavaVersion rather than a boolean with a giant name that sounds more complicated than it is.

This refactor will be done as part of Java 21 support

[Abacn]

Gradle 8.4 just released: https://docs.gradle.org/8.4/release-notes.html support compile and test with Java 21 now

[Abacn]

PreCommit added and passed on master branch: https://github.com/apache/beam/actions/runs/6709013800/job/18231112331

mark this task as fixed for now.

There are indeed followup works, e.g.

• Complete all PostCommits when runners (e.g. Flink Spark, etc) support Java21
• [Task]: Compile Java Examples Main on Java 11/17/21 when run Java Example Tests #28967 Compile Java Examples Main on Java 11/17/21 when run Java Example Tests