Complete Java 24 compatibility fix by backporting UnknownType workaround#6740
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timtebeek merged 1 commit intoopenrewrite:mainfrom Feb 14, 2026
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This completes the Java 24 compatibility work started in PR openrewrite#6725 by backporting the isUnknownType() helper method that was removed during the May 2025 simplification (commit 08b08ab). Background: - April 2025: JDK 24 support added with reflection-based workarounds - May 2025: Workarounds removed in "simplification" (commit 08b08ab) - February 2026: DocCommentTable fix backported in PR openrewrite#6725 - This PR: Backports the missing UnknownType fix Problem: Java 24 removed the Type.UnknownType class from javac internals. Direct instanceof Type.UnknownType checks cause NoClassDefFoundError at runtime on Java 24. Solution: Use reflection to check the class name at runtime instead of compile-time instanceof checks. This allows the code to work on both Java 21-23 (where the class exists) and Java 24+ (where it doesn't). Changes: - ReloadableJava21TypeMapping.java: Added isUnknownType() helper, replaced 3 instanceof checks - ReloadableJava21TypeSignatureBuilder.java: Replaced 2 instanceof checks Testing: Verified on spring-petclinic project with Java 24.0.2. Type attribution works correctly, ChangeType and ChangePackage recipes execute successfully, and migrated code compiles without errors. Fixes: openrewrite#6644 Related: openrewrite#6725, commit 08b08ab
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Thanks for the helpful links back to older commits that had introduced the same. Hope this is the final bit we need to restore Gradle 8.x on newer Java versions.
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Background:
Problem:
Java 24 removed the Type.UnknownType class from javac internals. Direct instanceof Type.UnknownType checks cause NoClassDefFoundError at runtime on Java 24.
Solution:
Use reflection to check the class name at runtime instead of compile-time instanceof checks. This allows the code to work on both Java 21-23 (where the class exists) and Java 24+ (where it doesn't).
Changes:
Testing:
Verified on spring-petclinic project with Java 24.0.2. Type attribution works correctly, ChangeType and ChangePackage recipes execute successfully, and migrated code compiles without errors.