[JAMES-3961] Migrate code base to JDK21

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.9.0
• Assignee: Unassigned
• Reporter: René Cordier
• Created: 13/Nov/23 07:44
• Updated: 03/Apr/24 05:02
• Resolved: 03/Apr/24 05:02

Description

The community seems in favor of adopting JDK 21 and migrating the code base to it. Multiple reasons for it:

• JDK 11 reached officially EOL 
• JDK 21 is the latest LTS
• multiple new features like records (bye bye boilerplates on POJOs), pattern matching, better GC, better thread management, ...

Few things to keep in mind as well:

• should we switch our modules to Jigsaw modules?
• should we maintain a JDK11 version in parallel for letting time for everybody to do the switch?

How:

• ADR explaining the change
• switch the JDK to 21 in the code base
• modify the code to get a green build with minimal changes first
• update documentation accordingly
• can refactoring things little by little after (like switching to records for POJOs for example)

Issue Links

• links to: GitHub Pull Request #1833
• links to: GitHub Pull Request #1939
• links to: GitHub Pull Request #2148
• links to: GitHub Pull Request #2171