Avoid retaining class files in annotation metadata - #37112
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ClassFileAnnotationDelegate passed the raw java.lang.classfile Annotation to MergedAnnotation.of() as the annotation source. That annotation holds a Utf8Entry, so retaining the metadata of an annotated class also retained its class file byte[], the parsed constant pool, and the class model. Store the declaring class name instead, as the ASM variant does. See spring-projectsgh-37111 Signed-off-by: Boris Perović <boris.perovic@sysdig.com>
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This is the Class-File versus ASM metadata overhead case from #36737, reported with a reproducer in #37111. On Java 24+
MetadataReaderFactoryDelegateselects the Class-File reader, which retains considerably more heap than the ASM one for the same classes.ClassFileAnnotationDelegatekeeps the rawjava.lang.classfile.Annotationas theMergedAnnotationsource. That annotation holds aUtf8Entry, so retaining the metadata of an annotated class also retains its class filebyte[], the parsed constant pool, and the class model. This stores the declaring class name instead, which is whatSimpleAnnotationMetadataReadingVisitor.Sourceholds on the ASM path.Measured with the reproducer (Temurin 25.0.3, spring-core 7.0.8):
SimpleMetadataReaderFactory(ASM)ClassFileMetadataReaderFactorybeforeClassFileMetadataReaderFactoryafterIn a large application's test context this took the retained size of a single
DefaultListableBeanFactoryfrom 128.4 MB to 53.4 MB. Forcing the ASM reader in the same build, by copyingMetadataReaderFactoryDelegateinto the project as suggested here, gives 46.1 MB.The difference that is left is not addressed here.
ClassFileMethodMetadataholdsAccessFlagsandMethodTypeDescobjects andClassFileAnnotationMetadataoneAccessFlags, whereSimpleMethodMetadataandSimpleAnnotationMetadatakeep plainintandStringvalues instead. #36978 already makes that change forClassFileMethodMetadata. Once both are changed, the reproducer matches the ASM baseline of 12.3 MB and the test context mentioned above comes to 46.9 MB.