Support for Java 21

[manusa]

Description

Java 21 has been released on the 19th of September 2023.

Update our base images to be Java 21 compatible.

• feat: Tomcat 9 based on Java 21 jkube-images#26
• feat: Tomcat 10 based on Java 21 jkube-images#25
• feat(jkube-java): support for Java 21 jkube-images#36
• Jetty
  Requires Add Java 21 image variants jetty/jetty.docker#177
  feat(jkube-jetty): support for Java 21 jkube-images#40
• Karaf
  Karaf 4.4.4 doesn't have full support for Java 21 org.osgi.service.blueprint.container.ComponentDefinitionException: java.lang.IllegalArgumentException: Invalid Java version 65 .
  Need to wait for Karaf 4.5.x
  feat(jkube-karaf): support for Java 21 jkube-images#37
  https://lists.apache.org/thread/8rynxznzztjplf8454njsjgzl8o0ojrf
  https://issues.apache.org/jira/browse/ARIES-2125
  [ARIES-2125] Add JDK 20 and 21 support apache/aries#241
  ARIES-2126: Update ASM to 9.5 apache/aries#242
  ARIES-2127: Add constants for Java 20/21 apache/aries#243
  https://lists.apache.org/thread/3vt19g1r4w6mcoqtpxxnsrsz2h4h69zw
  Support Java 21 in Builder.JavaVersion apache/karaf#1810

[manusa]

At this moment, there are no packages available for any of our base images

[marcindz88]

Hi there, what is the status of this issue?
When can we expect a version that supports java 21?

[manusa]

We'll deliver this in next minor version release.

However, we'll likely update and release our base images this week.
Until the JKube release is complete, you should still be able to switch the base image by using the jkube.generator.from generator option.

[manusa]

Leaving this on hold until #2381 gets merged or before we plan our next release