Feature request: recipe for migrating to Java 21

[matsev]

What problem are you trying to solve?

Recipe for automated migration to Java 21

Describe the solution you'd like

A recipe that automates Java migration from version 17 to 21, c.f. existing Java migration recipies

Have you considered any alternatives or workarounds?

No

Additional context

• Migrate to sequenced collections in Java 21 / JEP 431 #243
• Allow migrations to Java 21 #297
• Pattern Matching for switch in Java 21 / JEP 411 #306

Are you interested in contributing this feature to OpenRewrite?

Not at the moment

[timtebeek]

hi @matsev ; thanks for logging this request here! As you saw we already had two PRs related to Java 21

• Allow migrations to Java 21 #297
• Migrate to sequenced collections in Java 21 / JEP 431 #243

We're right now waiting for this issue & Gradle 8.4 before we're (easily) actually able to continue work on Java 21:

• Support running with Java 21 gradle/gradle#25574
• https://docs.gradle.org/8.4-rc-1/release-notes.html

Are there any particular migration recipes for Java 21 that you're looking forward to? It might make sense to log those as separate issues with links to the JEPs / release notes, as that makes it easier pick those up and close an issue.

We'd also need to add a Java 21 specific parser, similar to the Java 8, 11 and 17 parsers in OpenRewrite/rewrite. That way you're not stuck on Java 21 without OpenRewrite support. Also best tracked as a separate issue I suppose.

[matsev]

@timtebeek Thanks for your reply. Sequenced collection was the first thing that crossed my mind, but after looking at the Java 21 release notes I decided to create another ticket for JEP 441: Pattern Matching for switch (and possibly also for the related JEP 440: Record Patterns), please see #306

[timtebeek]

Thanks a lot! Helps to have them targeted to a particular use case, and thanks for the detail in reporting

• Pattern Matching for switch in Java 21 / JEP 411 #306

[timtebeek]

Now using gradle 8.4 here and in rewrite core, for Java 21 support; one step closer.

[timtebeek]

We now have a decent first set of recipes to migrate to Java 21:
https://docs.openrewrite.org/recipes/java/migrate/upgradetojava21

Closing this issue in favor of individual issues for further migration recipes.