Stop implementing SynthesizedAnnotation in annotation proxies #29041
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sbrannen
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This was referenced Sep 1, 2022
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Since Spring no longer adds the SynthesizedAnnotation interface to the JDK dynamic proxy used to synthesize an annotation, this commit officially deprecates SynthesizedAnnotation and related methods in RuntimeHintsUtils. See spring-projectsgh-29041, spring-projectsgh-29054 Closes spring-projectsgh-29053
This was referenced Sep 2, 2022
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Overview
This PR has two commits: one that stops using
SynthesizedAnnotationand a second that deprecatesSynthesizedAnnotation.If we decide to get rid of
SynthesizedAnnotation, we can subsequently remove it completely for Spring Framework 6.0.Discussion
SynthesizedAnnotationwas originally introduced as a convenience for easily detecting if an annotation had been synthesized by Spring via a simpleif (myAnnotation instanceof SynthesizedAnnotation)check.However, the introduction of
SynthesizedAnnotationin the JDK proxy for an annotation results in a separate proxy class for Spring's synthesized annotations, and this causes issues with GraalVM native images since users and framework developers must always ensure that the additional proxy classes are registered.This PR completely removes the use of
SynthesizedAnnotationin synthesized proxies which allows the JDK proxy class for the annotation to be reused within a GraalVM native image. See this project for a demonstration.Instead of checking if an annotation implements
SynthesizedAnnotation(to determine if the annotation needs to be synthesized), the PR uses aProxy.getInvocationHandler(annotation) instanceof SynthesizedMergedAnnotationInvocationHandler)check to determine if Spring synthesized the annotation.Drawbacks
At one point in 2015, @jhoeller used
Proxy.getInvocationHandlerto perform the "is synthesized" check; however, he reverted that due to #18402. See #18402 (comment) for details.Related Issues
Deliverables
Proxy.getInvocationHandlerwork without negative side effects such as those raised in #18402