Introduce support for synthesizing AnnotationAttributes into an annotation [SPR-13067]

[spring-projects-issues]

Sam Brannen opened SPR-13067 and commented

This issue picks up where #16137 and #16138 left off, with the primary goal of providing support for synthesizing an annotation from merged AnnotationAttributes like those returned from the getAnnotationAttributes(\*) and findAnnotationAttributes(\*) methods in AnnotatedElementUtils.

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Issue Links:

• Introduce synthesized annotation alternative to getAnnotationAttributes() in AnnotatedElementUtils [SPR-13082] #17673 Introduce synthesized annotation alternative to getAnnotationAttributes() in AnnotatedElementUtils ("is depended on by")
• Introduce unified support for declaring and looking up annotation attribute aliases [SPR-11512] #16137 Introduce unified support for declaring and looking up annotation attribute aliases
• Introduce support for explicit annotation attribute overrides [SPR-11513] #16138 Introduce support for explicit annotation attribute overrides
• Introduce a comprehensive programming model for meta-annotation support [SPR-11511] #16136 Introduce a comprehensive programming model for meta-annotation support

[spring-projects-issues]

Sam Brannen commented

The "holy grail of annotation processing" is in the air... ;)

I have pushed a working prototype for this issue to a #17659 feature branch.

Fee free to follow along or make comments!

[spring-projects-issues]

Sam Brannen commented

Update: the latest and greatest has been pushed to #17659.

Feedback is welcome!

[spring-projects-issues]

Sam Brannen commented

This has been implemented as described in the comments for GitHub commit e30c9b2:

Synthesize annotation from a map of attributes

Spring Framework 4.2 RC1 introduced support for synthesizing an
annotation from an existing annotation in order to provide additional
functionality above and beyond that provided by Java. Specifically,
such synthesized annotations provide support for @AliasFor semantics.
As luck would have it, the same principle can be used to synthesize an
annotation from any map of attributes, and in particular, from an
instance of AnnotationAttributes.

The following highlight the major changes in this commit toward
achieving this goal.

• Introduced AnnotationAttributeExtractor abstraction and refactored
  SynthesizedAnnotationInvocationHandler to delegate to an
  AnnotationAttributeExtractor.

• Extracted code from SynthesizedAnnotationInvocationHandler into new
  AbstractAliasAwareAnnotationAttributeExtractor and
  DefaultAnnotationAttributeExtractor implementation classes.

• Introduced MapAnnotationAttributeExtractor for synthesizing an
  annotation that is backed by a map or AnnotationAttributes instance.

• Introduced a variant of synthesizeAnnotation() in AnnotationUtils
  that accepts a map.

• Introduced findAnnotation(*) methods in AnnotatedElementUtils that
  synthesize merged AnnotationAttributes back into an annotation of the
  target type.

The following classes have been refactored to use the new support for
synthesizing AnnotationAttributes back into an annotation.

• ApplicationListenerMethodAdapter
• TestAnnotationUtils
• AbstractTestContextBootstrapper
• ActiveProfilesUtils
• ContextLoaderUtils
• DefaultActiveProfilesResolver
• DirtiesContextTestExecutionListener
• TestPropertySourceAttributes
• TestPropertySourceUtils
• TransactionalTestExecutionListener
• MetaAnnotationUtils
• MvcUriComponentsBuilder
• RequestMappingHandlerMapping

In addition, this commit also includes changes to ensure that arrays
returned by synthesized annotations are properly cloned first.