Walk the entire hierarchy of ClassLoaders, releasing memory for the

current webapp from each copy of LogFactory found.


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/logging/trunk@370464 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/commons/logging/impl/ServletContextCleaner.java

@@ -17,8 +17,11 @@
 
 package org.apache.commons.logging.impl;
 
-import javax.servlet.ServletContextListener;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+
 import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
 
 import org.apache.commons.logging.LogFactory;
 
@@ -49,13 +52,55 @@ import org.apache.commons.logging.LogFactory;
 
 public class ServletContextCleaner implements ServletContextListener {
 
+    private Class[] RELEASE_SIGNATURE = {ClassLoader.class};
+    
     /**
      * Invoked when a webapp is undeployed, this tells the LogFactory
      * class to release any logging information related to the current
      * contextClassloader.
      */
     public void contextDestroyed(ServletContextEvent sce) {
-        LogFactory.release(Thread.currentThread().getContextClassLoader());
+        ClassLoader tccl = Thread.currentThread().getContextClassLoader();
+
+        Object[] params = new Object[1];
+        params[0] = tccl;
+
+        // Walk up the tree of classloaders, finding all the available
+        // LogFactory classes and releasing any objects associated with
+        // the tccl (ie the webapp).
+        ClassLoader loader = tccl;
+        while (loader != null) {
+            // Load via the current loader. Note that if the class is not accessable
+            // via this loader, but is accessable via some ancestor then that class
+            // will be returned.
+            try {
+                Class logFactoryClass = loader.loadClass("org.apache.commons.logging.LogFactory");
+                Method releaseMethod = logFactoryClass.getMethod("release", RELEASE_SIGNATURE);
+                releaseMethod.invoke(null, params);
+                loader = logFactoryClass.getClassLoader().getParent();
+            } catch(ClassNotFoundException ex) {
+                // Neither the current classloader nor any of its ancestors could find
+                // the LogFactory class, so we can stop now.
+                loader = null;
+            } catch(NoSuchMethodException ex) {
+                // This is not expected; every version of JCL has this method
+                System.err.println("LogFactory instance found which does not support release method!");
+                loader = null;
+            } catch(IllegalAccessException ex) {
+                // This is not expected; every ancestor class should be accessable
+                System.err.println("LogFactory instance found which is not accessable!");
+                loader = null;
+            } catch(InvocationTargetException ex) {
+                // This is not expected
+                System.err.println("LogFactory instance release method failed!");
+                loader = null;
+            }
+        }
+        
+        // Just to be sure, invoke release on the LogFactory that is visible from
+        // this ServletContextCleaner class too. This should already have been caught
+        // by the above loop but just in case...
+        LogFactory.release(tccl);
     }
     
     /**