Epic Goal

Update Jenkins to use the next supported LTS JDK by default - JDK 21

Why is this important?

JDK 11 EOL is end of Q3 2024 - customers need time to test Jenkins with JDK 21.
JDK 21 is also available, and will be the next Java version with "extended" LTS support from the OpenJDK community (akin to Java 8).

Scenarios

1. Run Jenkins with JDK 21
2. Build Java apps with JDK 21

Acceptance Criteria (Mandatory)

• Jenkins uses JDK 21 by default
• Jenkins plugins compile with JDK 21
• Customers can downgrade the JDK to Java 11

Stretch/optional goal: allow the JDK to be upgraded to 21

Dependencies (internal and external)

TBD

Previous Work (Optional):

TBD

Open questions::

TBD

Done Checklist

• Acceptance criteria are met
• Non-functional properties of the Feature have been validated (such as performance, resource, UX, security or privacy aspects)
• User Journey automation is delivered
• Support and SRE teams are provided with enough skills to support the feature in production environment