/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2007, Red Hat Middleware LLC, and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.jboss.web.tomcat.service.session;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.NotSerializableException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

/**
 * Diagnostic tool to help identify when non-serializable objects are
 * placed in a web session.  To use, place this class on the webapp's
 * classpath and add the following to <code>web.xml</code>:
 * <p>
 * <code><listener><listener-class>org.jboss.web.tomcat.service.session.NonSerializableAttributeTester</listener-class></listener></code>
 * </p>
 * 
 * @author <a href="brian.stansberry@jboss.com">Brian Stansberry</a>
 * @version $Revision: 1.1 $
 */
public class NonSerializableAttributeTester 
   implements HttpSessionAttributeListener
{

   public NonSerializableAttributeTester()
   {
      super();
   }

   public void attributeAdded(HttpSessionBindingEvent event)
   {
      testAttributeSerializability(event.getName(), event.getValue());
   }

   public void attributeRemoved(HttpSessionBindingEvent event)
   {
      // do nothing
   }

   public void attributeReplaced(HttpSessionBindingEvent event)
   {
      testAttributeSerializability(event.getName(), event.getValue());
   }
   
   private void testAttributeSerializability(String name, Object value)
   {
      if (!testSerializability(value))
      {
         System.out.println(name + " of type " + value.getClass() + 
                            " cannot be serialized");
         testRecursively(value);
      }
      
   }
   
   private boolean testSerializability(Object obj)
   {
      if (obj == null)
         return true;
      
      if (!(obj instanceof Serializable))
      {
         return false;
      }
      else
      {
         ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
         try
         {
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(obj);
            oos.close();
         }
         catch (NotSerializableException io)
         {
            return false;
         }
         catch (IOException io)
         {
            System.out.println("Unexpected IOException");
            io.printStackTrace(System.out);
         }
      }
      
      return true;
   }
   
   private void testRecursively(Object obj)
   {
      if (obj instanceof Collection)
      {
         testCollectionSerializability((Collection) obj);
      }
      else if (obj instanceof Map)
      {
         testMapSerializability((Map) obj);
      }
      
   }
   
   private void testCollectionSerializability(Collection coll)
   {
      System.out.println("Testing Collection elements");
      int i = 0;
      for (Iterator iter = coll.iterator(); iter.hasNext(); i++)
      {
         Object obj = iter.next();
         if (!(testSerializability(obj)))
         {
            System.out.println("Element " + i + " of type " + obj.getClass() +
                               " cannot be serialized");
            testRecursively(obj);
         }
      }
   }
   
   private void testMapSerializability(Map map)
   {
      System.out.println("Testing Map entries");
      for (Iterator iter = map.entrySet().iterator(); iter.hasNext();)
      {
         Map.Entry entry = (Map.Entry) iter.next();
         if (!testSerializability(entry.getKey()))
         {
            System.out.println("Map Key " + entry.getKey() + " of type " +
                  entry.getKey().getClass() + " cannot be serialized");
            testRecursively(entry.getKey());
         }
         else if (!testSerializability(entry.getValue()))
         {
            System.out.println("Map value under Key " + entry.getKey() + " of type " +
                  entry.getValue().getClass() + " cannot be serialized");
            testRecursively(entry.getValue());
         }
      }
   }

}