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.

Issue: SPR-13067

Prior to this commit, when a nested array of annotations was
synthesized while adapting values within an AnnotationAttributes map,
the array was improperly replaced with an array of type Annotation[]
instead of an array of the concrete annotation type, which can lead to
unexpected run-time exceptions.

This commit fixes this bug by replacing annotations in the existing
array with synthesized versions of those annotations, thereby retaining
the original array's component type.

Issue: SPR-13077

Issue: SPR-11513

Issue: SPR-11512

Issue: SPR-11512

Issue: SPR-11512

Issue: SPR-11512

Issue: SPR-11512

This commit also introduces a cache for attribute alias metadata.

Issue: SPR-11512

Issue: SPR-13064

Issue: SPR-11512

Issue: SPR-11512

This commit introduces first-class support for aliases for annotation
attributes. Specifically, this commit introduces a new @AliasFor
annotation that can be used to declare a pair of aliased attributes
within a single annotation or an alias from an attribute in a custom
composed annotation to an attribute in a meta-annotation.

To support @AliasFor within annotation instances, AnnotationUtils has
been overhauled to "synthesize" any annotations returned by "get" and
"find" searches. A SynthesizedAnnotation is an annotation that is
wrapped in a JDK dynamic proxy which provides run-time support for
@AliasFor semantics. SynthesizedAnnotationInvocationHandler is the
actual handler behind the proxy.

In addition, the contract for @AliasFor is fully validated, and an
AnnotationConfigurationException is thrown in case invalid
configuration is detected.

For example, @ContextConfiguration from the spring-test module is now
declared as follows:

    public @interface ContextConfiguration {

        @AliasFor(attribute = "locations")
        String[] value() default {};

        @AliasFor(attribute = "value")
        String[] locations() default {};

        // ...
    }

The following annotations and their related support classes have been
modified to use @AliasFor.

- @ManagedResource
- @ContextConfiguration
- @ActiveProfiles
- @TestExecutionListeners
- @TestPropertySource
- @Sql
- @ControllerAdvice
- @RequestMapping

Similarly, support for AnnotationAttributes has been reworked to
support @AliasFor as well. This allows for fine-grained control over
exactly which attributes are overridden within an annotation hierarchy.
In fact, it is now possible to declare an alias for the 'value'
attribute of a meta-annotation.

For example, given the revised declaration of @ContextConfiguration
above, one can now develop a composed annotation with a custom
attribute override as follows.

    @ContextConfiguration
    public @interface MyTestConfig {

        @AliasFor(
           annotation = ContextConfiguration.class,
           attribute = "locations"
        )
        String[] xmlFiles();

        // ...
    }

Consequently, the following are functionally equivalent.

- @MyTestConfig(xmlFiles = "test.xml")
- @ContextConfiguration("test.xml")
- @ContextConfiguration(locations = "test.xml").

Issue: SPR-11512, SPR-11513

Issue: SPR-12926

Prior to this commit, the documentation in AnnotationUtils was
inconsistent, and at times even misleading, with regard to finding
annotations that are "present" or "directly present" on annotated
elements.

This commit defines the terminology used within AnnotationUtils and
introduces the explicit notion of "meta-present" to denote that
annotations are present within annotation hierarchies above annotated
elements.

Issue: SPR-13030

This commit improves the documentation for AnnotationUtils and
AnnotatedElementUtils by explaining that the scope of most annotation
searches is limited to finding the first such annotation, resulting in
additional such annotations being silently ignored.

Issue: SPR-13015

This commit picks up where SPR-11483 left off, with the goal of
eliminating all unnecessary inspection of core JDK annotations in
Spring's annotation search algorithms in AnnotatedElementUtils and
AnnotationMetadataReadingVisitor.

Issue: SPR-12989

This commit introduces support for finding annotations on abstract,
bridge, and interface methods in AnnotatedElementUtils.

 - Introduced dedicated findAnnotationAttributes() methods in
   AnnotatedElementUtils that provide first-class support for
   processing methods, class hierarchies, interfaces, bridge methods,
   etc.

 - Introduced find/get search algorithm dichotomy in
   AnnotatedElementUtils which is visible in the public API as well as
   in the internal implementation. This was necessary in order to
   maintain backwards compatibility with the existing API (even though
   it was undocumented).

 - Reverted all recent changes made to the "get semantics" search
   algorithm in AnnotatedElementUtils in order to ensure backwards
   compatibility, and reverted recent changes to
   JtaTransactionAnnotationParser and SpringTransactionAnnotationParser
   accordingly.

 - Documented internal AnnotatedElementUtils.Processor<T> interface.

 - Enabled failing tests and introduced
   findAnnotationAttributesFromBridgeMethod() test in
   AnnotatedElementUtilsTests.

 - Refactored ApplicationListenerMethodAdapter.getCondition() and
   enabled failing test in TransactionalEventListenerTests.

 - AnnotationUtils.isInterfaceWithAnnotatedMethods() is now package
   private.

Issue: SPR-12738, SPR-11514, SPR-11598

Prior to this commit, the search algorithm used by the
findAnnotation(Method, Class) method in AnnotationUtils only found
direct annotations or direct meta-annotations (i.e., one level of
meta-annotations).

This commit reworks the search algorithm so that it supports arbitrary
levels of meta-annotations on methods. To make this possible, a new
findAnnotation(AnnotatedElement, Class) method has been introduced in
AnnotationUtils.

This fix also allows for the @Ignore'd tests in
TransactionalEventListenerTests to be re-enabled.

Issue: SPR-12941

Issue: SPR-12940

Also refines logIntrospectionFailure to just log at debug level for meta-annotation introspection failures.

Issue: SPR-12889

AnnotationUtils.getAnnotationAttributes makes Method accessible (analogous to AnnotationUtils.getValue)

Issue: SPR-12858

Issue: SPR-12604

This commit updates the Javadoc for findAnnotation() to reflect recent
changes to the algorithm it implements.

Issue: SPR-12493

Normalized AnnotationAttributesReadingVisitor class layout and improved diagnostics through delegating to AnnotationUtils

Issue: SPR-12387

Issue: SPR-12325

AnnotationUtils favors local composed annotations over interface annotations and consistently logs introspection failures via lazily initialized logger

Issue: SPR-12355
Issue: SPR-12325
Issue: SPR-12329

Issue: SPR-12065

ReflectionUtils caches Class.getDeclaredMethods() results; AnnotationUtils caches findAnnotation results

Issue: SPR-11882

AnnotationUtils defensively catches and logs unexpected exceptions from retrieval attempts (proceeding like the annotation wasn't there)

Issue: SPR-11874

AnnotationUtils defensively catches unexpected exceptions from retrieval attempts (proceeding like the annotation wasn't there)

This is analogous to what the JVM does for cases where the annotation type itself isn't present on the classpath. We're effectively extending that policy to values referenced within an annotation declaration.

Issue: SPR-11874