Avoid unnecessary inspection of meta-annotations on Java annotations [SPR-11483]

[spring-projects-issues]

Sam Brannen opened SPR-11483 and commented

Status Quo

Several annotation-based search algorithms within the Spring Framework inspect meta-annotations on Java annotations as part of their recursive search processes. However, such inspection is unnecessary simply because any annotation on a Java annotation (e.g., @Retention, @Target, @Documented, etc.) will be irrelevant to the current search. In other words, a Spring annotation or a custom user annotation will never be present on a Java annotation. So it makes no sense to look for it there.

Deliverables

For each of the affected search algorithms in the following classes, do not inspect meta-annotations on annotations from the java.lang.annotation package.

1. AnnotationUtils
2. AnnotatedElementUtils
3. MetaAnnotationUtils

---

Affects: 4.0 GA

Issue Links:

• Eliminate inspection of meta-annotations on Java annotations [SPR-12989] #17580 Eliminate inspection of meta-annotations on Java annotations ("is depended on by")

[spring-projects-issues]

Sam Brannen commented

This has been addressed as described in the comments for GitHub commit 979c483:

Do not inspect meta-annotations on Java annotations

This commit introduces a new isInJavaLangAnnotationPackage(Annotation)
method in AnnotationUtils. This method is now used in AnnotationUtils,
AnnotatedElementUtils, and MetaAnnotationUtils to ensure that search
algorithms do no search for meta-annotations on annotations in the
"java.lang.annotation" package.

The following are some empirical results from this change:

• The number of times that the findAnnotation(Class,Class,Set) method in
  AnnotationUtils is recursively invoked while executing
  AnnotationUtilsTests drops from 51 to 29.

• The number of times that the process(AnnotatedElement) method in
  AnnotationUtils.AnnotationCollector is recursively invoked while
  executing AnnotationUtilsTests.getRepeatableFromMethod() drops
  from 16 to 2.

• The number of times that the doProcess() method in
  AnnotatedElementUtils is recursively invoked while executing the
  "getAnnotationAttributes() On MetaCycleAnnotatedClass with missing
  target meta-annotation" test in AnnotatedElementUtilsTests drops
  from 23 to 5.

• The number of times that the findAnnotationDescriptor(Class,Set,Class)
  method in MetaAnnotationUtils is recursively invoked while executing
  the "findAnnotationDescriptor() on MetaCycleAnnotatedClass with
  missing target meta-annotation" test in MetaAnnotationUtilsTests drops
  from 16 to 8.