WW-5537 Resolve classloader/memory leaks during Tomcat hot deployment (#1632)

* WW-5537 Add InternalDestroyable and ContextAwareDestroyable interfaces

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 ContainerHolder: ThreadLocal with AtomicLong generation counter

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 FinalizableReferenceQueue: volatile instance, join, classloader null

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 ScopeInterceptor.clearLocks: add synchronized block

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 CompoundRootAccessor, DefaultFileManager: implement InternalDestroyable

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Add InternalDestroyable adapter classes for static cache cleanup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Register InternalDestroyable beans in struts-beans.xml

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 JSON plugin: add JSONCacheDestroyable for BeanInfo cache cleanup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Dispatcher.cleanup: refactor into focused methods with InternalDestroyable discovery

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Rewrite DispatcherCleanupTest for InternalDestroyable discovery

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Add log4j-web for proper Log4j2 lifecycle in Servlet container

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Dispatcher.destroyObjectFactory: add early return on null, use pattern matching

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Fix @since annotations: 7.1.0 -> 7.2.0

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Add Container.destroy() to clear internal caches on undeploy

Container now exposes a destroy() method that clears factories, injectors,
constructors, and ThreadLocals. This releases Class<?> keys and JDK
DelegatingClassLoader instances that pin the webapp classloader.

DefaultConfiguration.destroy() calls container.destroy() and
reloadContainer() delegates to destroy() to avoid duplication.

Also fixes JSONCacheDestroyable referencing non-existent DefaultJSONWriter
(renamed to StrutsJSONWriter).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Fix Container.destroy(): don't clear factories, don't call from reloadContainer

factories must remain intact because existing code holds direct
references to the Container after destroyConfiguration() and expects
it to still resolve dependencies (e.g. during configuration reload).

reloadContainer() reverted to clearing packageContexts/loadedFileNames
directly — calling destroy() there nulled the container reference and
cleared state needed during the bootstrap transition.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Restore destroy() call in reloadContainer()

The test failures were caused by factories.clear() in
Container.destroy(), not by calling destroy() from reloadContainer().
Now that factories.clear() is removed, destroy() is safe to call
here — it clears packageContexts, loadedFileNames, and the container's
reflection caches in one place.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* WW-5537 Fix Sonar issues: thread-safe FinalizableReferenceQueue, empty method comments

- Replace volatile field with AtomicReference in FinalizableReferenceQueue
  for proper thread safety using getAndSet()
- Add comments to empty destroy() implementations in test mocks
- Replace deprecated new URL() with URI.toURL() in DispatcherCleanupTest
- Add comments to empty listener methods in DispatcherCleanupTest

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

apps/showcase/pom.xml

@@ -119,6 +119,10 @@
             <groupId>org.apache.logging.log4j</groupId>
             <artifactId>log4j-slf4j-impl</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.logging.log4j</groupId>
+            <artifactId>log4j-web</artifactId>
+        </dependency>
 
         <dependency>
            <groupId>org.sitemesh</groupId>