// ========================================================================
   // Copyright (c) 2011 Mort Bay Consulting Pty. Ltd.
   // ------------------------------------------------------------------------
   // All rights reserved. This program and the accompanying materials
   // are made available under the terms of the Eclipse Public License v1.0
   // and Apache License v2.0 which accompanies this distribution.
   // The Eclipse Public License is available at
   // http://www.eclipse.org/legal/epl-v10.html
   // The Apache License v2.0 is available at
  // http://www.opensource.org/licenses/apache2.0.php
  // You may elect to redistribute this code under either of these licenses.
  // ========================================================================
  
  package org.eclipse.jetty.servlet.listener;
  
  import java.lang.reflect.Field;
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.util.Iterator;
  import java.util.concurrent.ConcurrentHashMap;
  
  import javax.servlet.ServletContextEvent;
  import javax.servlet.ServletContextListener;
  
  import org.eclipse.jetty.util.Loader;
  import org.eclipse.jetty.util.log.Log;
  import org.eclipse.jetty.util.log.Logger;
  
  /**
   * ELContextCleaner
   *
   * Clean up BeanELResolver when the context is going out
   * of service:
   * 
   * See http://java.net/jira/browse/GLASSFISH-1649
   * See https://bugs.eclipse.org/bugs/show_bug.cgi?id=353095
   */
  public class ELContextCleaner implements ServletContextListener
  {
      private static final Logger LOG = Log.getLogger(ELContextCleaner.class);
  
  
      public void contextInitialized(ServletContextEvent sce)
      {
      }
  
      public void contextDestroyed(ServletContextEvent sce)
      {
          try
          {
              //Check that the BeanELResolver class is on the classpath
              Class beanELResolver = Loader.loadClass(this.getClass(), "javax.el.BeanELResolver");
  
              //Get a reference via reflection to the properties field which is holding class references
              Field field = getField(beanELResolver);
  
              //Get rid of references
              purgeEntries(field);
              
              LOG.info("javax.el.BeanELResolver purged");
          }
          
          catch (ClassNotFoundException e)
          {
              //BeanELResolver not on classpath, ignore
          }
          catch (SecurityException e)
          {
              LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
          }
          catch (IllegalArgumentException e)
          {
              LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
          }
          catch (IllegalAccessException e)
          {
              LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
          }
          catch (NoSuchFieldException e)
          {
              LOG.warn("Cannot purge classes from javax.el.BeanELResolver", e);
          }
         
      }
  
  
      protected Field getField (Class beanELResolver) 
      throws SecurityException, NoSuchFieldException
      {
          if (beanELResolver == null)
              return  null;
  
          return beanELResolver.getDeclaredField("properties");
      }
  
      protected void purgeEntries (Field properties) 
      throws IllegalArgumentException, IllegalAccessException
      {
          if (properties == null)
             return;
 
         if (!properties.isAccessible())
             properties.setAccessible(true);
 
         ConcurrentHashMap map = (ConcurrentHashMap) properties.get(null);
         if (map == null)
             return;
         
         Iterator<Class> itor = map.keySet().iterator();
         while (itor.hasNext()) 
         {
             Class clazz = itor.next();
             LOG.info("Clazz: "+clazz+" loaded by "+clazz.getClassLoader());
             if (Thread.currentThread().getContextClassLoader().equals(clazz.getClassLoader()))
             {
                 itor.remove();  
                 LOG.info("removed");
             }
             else
                 LOG.info("not removed: "+"contextclassloader="+Thread.currentThread().getContextClassLoader()+"clazz's classloader="+clazz.getClassLoader());
         }
     }
 }