/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *   http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  */

 package org.apache.myfaces.application.jsp;

 import org.apache.commons.collections.map.AbstractReferenceMap;

 import org.apache.commons.collections.map.ReferenceMap;

 import org.apache.commons.logging.Log;

 import org.apache.commons.logging.LogFactory;

 import org.apache.myfaces.application.MyfacesStateManager;

 import org.apache.myfaces.application.TreeStructureManager;

 import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;

 import org.apache.myfaces.renderkit.MyfacesResponseStateManager;

 import org.apache.myfaces.shared_impl.renderkit.RendererUtils;

 import org.apache.myfaces.shared_impl.util.MyFacesObjectInputStream;

 import javax.faces.FacesException;

 import javax.faces.FactoryFinder;

 import javax.faces.component.NamingContainer;

 import javax.faces.component.UIComponent;

 import javax.faces.component.UIViewRoot;

 import javax.faces.context.ExternalContext;

 import javax.faces.context.FacesContext;

 import javax.faces.render.RenderKit;

 import javax.faces.render.RenderKitFactory;

 import javax.faces.render.ResponseStateManager;

 import java.io.*;

 import java.lang.reflect.Method;

 import java.security.AccessController;

 import java.security.PrivilegedActionException;

 import java.security.PrivilegedExceptionAction;

 import java.util.*;

 import java.util.zip.GZIPInputStream;

 import java.util.zip.GZIPOutputStream;

 /**

  * Default StateManager implementation for use when views are defined

  * via tags in JSP pages.

  *

  * @author Thomas Spiegl (latest modification by $Author: lu4242 $)

  * @author Manfred Geiler

  * @version $Revision: 951800 $ $Date: 2010-06-05 21:07:42 -0500 (Sat, 05 Jun 2010) $

  */

 public class JspStateManagerImpl

     extends MyfacesStateManager

 {

     private static final Log log = LogFactory.getLog(JspStateManagerImpl.class);

     private static final String SERIALIZED_VIEW_SESSION_ATTR

             = JspStateManagerImpl.class.getName() + ".SERIALIZED_VIEW";

     private static final String SERIALIZED_VIEW_REQUEST_ATTR

             = JspStateManagerImpl.class.getName() + ".SERIALIZED_VIEW";

     private static final String RESTORED_SERIALIZED_VIEW_REQUEST_ATTR

     = JspStateManagerImpl.class.getName() + ".RESTORED_SERIALIZED_VIEW";

     /**

      * Only applicable if state saving method is "server" (= default).

      * Defines the amount (default = 20) of the latest views are stored in session.

      */

     @JSFWebConfigParam(defaultValue="20",since="1.1")

     private static final String NUMBER_OF_VIEWS_IN_SESSION_PARAM = "org.apache.myfaces.NUMBER_OF_VIEWS_IN_SESSION";

     /**

      * Default value for <code>org.apache.myfaces.NUMBER_OF_VIEWS_IN_SESSION</code> context parameter.

      */

     private static final int DEFAULT_NUMBER_OF_VIEWS_IN_SESSION = 20;

     /**

      * Only applicable if state saving method is "server" (= default).

      * If <code>true</code> (default) the state will be serialized to a byte stream before it is written to the session.

      * If <code>false</code> the state will not be serialized to a byte stream.

      */

     @JSFWebConfigParam(defaultValue="true",since="1.1")

     private static final String SERIALIZE_STATE_IN_SESSION_PARAM = "org.apache.myfaces.SERIALIZE_STATE_IN_SESSION";

     /**

      * Only applicable if state saving method is "server" (= default) and if <code>org.apache.myfaces.SERIALIZE_STATE_IN_SESSION</code> is <code>true</code> (= default).

      * If <code>true</code> (default) the serialized state will be compressed before it is written to the session.

      * If <code>false</code> the state will not be compressed.

      */

     @JSFWebConfigParam(defaultValue="true",since="1.1")

     private static final String COMPRESS_SERVER_STATE_PARAM = "org.apache.myfaces.COMPRESS_STATE_IN_SESSION";

     /**

      * Default value for <code>org.apache.myfaces.COMPRESS_STATE_IN_SESSION</code> context parameter.

      */

     private static final boolean DEFAULT_COMPRESS_SERVER_STATE_PARAM = true;

     /**

      * Default value for <code>org.apache.myfaces.SERIALIZE_STATE_IN_SESSION</code> context parameter.

      */

     private static final boolean DEFAULT_SERIALIZE_STATE_IN_SESSION = true;

     /**

      * Define the way of handle old view references(views removed from session), making possible to

      * store it in a cache, so the state manager first try to get the view from the session. If is it

      * not found and soft or weak ReferenceMap is used, it try to get from it.

      * <p>

      * Only applicable if state saving method is "server" (= default).

      * </p>

      * <p>

      * The gc is responsible for remove the views, according to the rules used for soft, weak or phantom

      * references. If a key in soft and weak mode is garbage collected, its values are purged.

      * </p>

      * <p>

      * By default no cache is used, so views removed from session became phantom references.

      * </p>

      * <ul> 

      * <li> off, no: default, no cache is used</li> 

      * <li> hard-soft: use an ReferenceMap(AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT)</li>

      * <li> soft: use an ReferenceMap(AbstractReferenceMap.SOFT, AbstractReferenceMap.SOFT, true) </li>

      * <li> soft-weak: use an ReferenceMap(AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAK, true) </li>

      * <li> weak: use an ReferenceMap(AbstractReferenceMap.WEAK, AbstractReferenceMap.WEAK, true) </li>

      * </ul>

      * 

      */

     @JSFWebConfigParam(defaultValue="off", expectedValues="off, no, hard-soft, soft, soft-weak, weak", since="1.2.5")

     private static final String CACHE_OLD_VIEWS_IN_SESSION_MODE = "org.apache.myfaces.CACHE_OLD_VIEWS_IN_SESSION_MODE";

     /**

      * This option uses an hard-soft ReferenceMap, but it could cause a 

      * memory leak, because the keys are not removed by any method

      * (MYFACES-1660). So use with caution.

      */

     private static final String CACHE_OLD_VIEWS_IN_SESSION_MODE_HARD_SOFT = "hard-soft";

     private static final String CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT = "soft";

     private static final String CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT_WEAK = "soft-weak";

     private static final String CACHE_OLD_VIEWS_IN_SESSION_MODE_WEAK = "weak";

     private static final String CACHE_OLD_VIEWS_IN_SESSION_MODE_OFF = "off";

     private static final int UNCOMPRESSED_FLAG = 0;

     private static final int COMPRESSED_FLAG = 1;

     private static final int JSF_SEQUENCE_INDEX = 0;

     private RenderKitFactory _renderKitFactory = null;

     public JspStateManagerImpl()

     {

         if (log.isTraceEnabled()) log.trace("New JspStateManagerImpl instance created");

     }

     protected Object getComponentStateToSave(FacesContext facesContext)

     {

         if (log.isTraceEnabled()) log.trace("Entering getComponentStateToSave");

         UIViewRoot viewRoot = facesContext.getViewRoot();

         if (viewRoot.isTransient())

         {

             return null;

         }

         Object serializedComponentStates = viewRoot.processSaveState(facesContext);

         //Locale is a state attribute of UIViewRoot and need not be saved explicitly

         if (log.isTraceEnabled()) log.trace("Exiting getComponentStateToSave");

         return serializedComponentStates;

     }

     /**

      * Return an object which contains info about the UIComponent type

      * of each node in the view tree. This allows an identical UIComponent

      * tree to be recreated later, though all the components will have

      * just default values for their members.

      */

     protected Object getTreeStructureToSave(FacesContext facesContext)

     {

         if (log.isTraceEnabled()) log.trace("Entering getTreeStructureToSave");

         UIViewRoot viewRoot = facesContext.getViewRoot();

         if (viewRoot.isTransient())

         {

             return null;

         }

         TreeStructureManager tsm = new TreeStructureManager();

         Object retVal = tsm.buildTreeStructureToSave(viewRoot);

         if (log.isTraceEnabled()) log.trace("Exiting getTreeStructureToSave");

         return retVal;

     }

     /**

      * Given a tree of UIComponent objects created the default constructor

      * for each node, retrieve saved state info (from either the client or

      * the server) and walk the tree restoring the members of each node

      * from the saved state information.

      */

     protected void restoreComponentState(FacesContext facesContext,

                                          UIViewRoot uiViewRoot,

                                          String renderKitId)

     {

         if (log.isTraceEnabled()) log.trace("Entering restoreComponentState");

         //===========================================

         // first, locate the saved state information

         //===========================================

         RenderKit renderKit = getRenderKitFactory().getRenderKit(facesContext, renderKitId);

         ResponseStateManager responseStateManager = renderKit.getResponseStateManager();

         Object serializedComponentStates;

         if (isSavingStateInClient(facesContext))

         {

             if (isLegacyResponseStateManager(responseStateManager))

             {

                 serializedComponentStates = responseStateManager.getComponentStateToRestore(facesContext);

             }

             else

             {

                 serializedComponentStates = responseStateManager.getState(facesContext, uiViewRoot.getViewId());

             }

             if (serializedComponentStates == null)

             {

                 log.error("No serialized component state found in client request!");

                 // mark UIViewRoot invalid by resetting view id

                 uiViewRoot.setViewId(null);

                 return;

             }

         }

         else

         {

             Integer serverStateId = getServerStateId((Object[]) responseStateManager.getState(facesContext, uiViewRoot.getViewId()));

             Object[] stateObj = (Object[])( (serverStateId == null)? null : getSerializedViewFromServletSession(facesContext, uiViewRoot.getViewId(), serverStateId) );

             if (stateObj == null)

             {

                  log.error("No serialized view found in server session!");

                 // mark UIViewRoot invalid by resetting view id

                 uiViewRoot.setViewId(null);

                 return;

             }

             SerializedView serializedView = new SerializedView(stateObj[0], stateObj[1]);

             serializedComponentStates = serializedView.getState();

             if (serializedComponentStates == null)

             {

                 log.error("No serialized component state found in server session!");

                 return;

             }

         }

         if (uiViewRoot.getRenderKitId() == null)

         {

             //Just to be sure...

             uiViewRoot.setRenderKitId(renderKitId);

         }

         // now ask the view root component to restore its state

         uiViewRoot.processRestoreState(facesContext, serializedComponentStates);

         if (log.isTraceEnabled()) log.trace("Exiting restoreComponentState");

     }

       protected Integer getServerStateId(Object[] state)

       {

         if (state != null)

         {

             Object serverStateId = state[JSF_SEQUENCE_INDEX];

             if (serverStateId != null)

             {

                 return Integer.valueOf((String) serverStateId, Character.MAX_RADIX);

             }

         }

         return null;

     }

     /**

      * See getTreeStructureToSave.

      */

     protected UIViewRoot restoreTreeStructure(FacesContext facesContext,

                                               String viewId,

                                               String renderKitId)

     {

         if (log.isTraceEnabled()) log.trace("Entering restoreTreeStructure");

         RenderKit rk = getRenderKitFactory().getRenderKit(facesContext, renderKitId);

         ResponseStateManager responseStateManager = rk.getResponseStateManager();

         UIViewRoot uiViewRoot;

         if (isSavingStateInClient(facesContext))

         {

             //reconstruct tree structure from request

             Object treeStructure = responseStateManager.getTreeStructureToRestore(facesContext, viewId);

             if (treeStructure == null)

             {

                 if (log.isDebugEnabled()) log.debug("Exiting restoreTreeStructure - No tree structure state found in client request");

                 return null;

             }

             TreeStructureManager tsm = new TreeStructureManager();

             uiViewRoot = tsm.restoreTreeStructure(treeStructure);

             if (log.isTraceEnabled()) log.trace("Tree structure restored from client request");

         }

         else

         {

             //reconstruct tree structure from ServletSession

             Integer serverStateId = getServerStateId((Object[]) responseStateManager.getState(facesContext, viewId));

             Object[] stateObj = (Object[])( (serverStateId == null)? null : getSerializedViewFromServletSession(facesContext, viewId, serverStateId) );

             if (stateObj == null)

             {

                 if (log.isDebugEnabled()) log.debug("Exiting restoreTreeStructure - No serialized view found in server session!");

                 return null;

             }

             SerializedView serializedView = new SerializedView(stateObj[0], stateObj[1]);

             Object treeStructure = serializedView.getStructure();

             if (treeStructure == null)

             {

                 if (log.isDebugEnabled()) log.debug("Exiting restoreTreeStructure - No tree structure state found in server session, former UIViewRoot must have been transient");

                 return null;

             }

             TreeStructureManager tsm = new TreeStructureManager();

             uiViewRoot = tsm.restoreTreeStructure(serializedView.getStructure());

             if (log.isTraceEnabled()) log.trace("Tree structure restored from server session");

         }

         if (log.isTraceEnabled()) log.trace("Exiting restoreTreeStructure");

         return uiViewRoot;

     }

     public UIViewRoot restoreView(FacesContext facesContext, String viewId, String renderKitId)

     {

         if (log.isTraceEnabled()) log.trace("Entering restoreView - viewId: "+viewId+" ; renderKitId: "+renderKitId);

         RenderKit renderKit = getRenderKitFactory().getRenderKit(facesContext, renderKitId);

         ResponseStateManager responseStateManager = renderKit.getResponseStateManager();

         Object state;

         if (isSavingStateInClient(facesContext))

         {

             if (log.isTraceEnabled()) log.trace("Restoring view from client");

             state = responseStateManager.getState(facesContext, viewId);

         }

         else

         {

             if (log.isTraceEnabled()) log.trace("Restoring view from session");

             Integer serverStateId = getServerStateId((Object[]) responseStateManager.getState(facesContext, viewId));

             state = (serverStateId == null) ? null : getSerializedViewFromServletSession(facesContext, viewId, serverStateId);

         }

         UIViewRoot uiViewRoot = null;

         if (state != null) {

             Object[] stateArray = (Object[])state;

             TreeStructureManager tsm = new TreeStructureManager();

             uiViewRoot = tsm.restoreTreeStructure(stateArray[0]);

             if (uiViewRoot != null) {

                 uiViewRoot.processRestoreState(facesContext, stateArray[1]);

             }

         }

         if (log.isTraceEnabled()) log.trace("Exiting restoreView - "+viewId);

         return uiViewRoot;

     }

     public SerializedView saveSerializedView(FacesContext facesContext) throws IllegalStateException

     {

         if (log.isTraceEnabled()) log.trace("Entering saveSerializedView");

         checkForDuplicateIds(facesContext, facesContext.getViewRoot(), new HashSet<String>());

         if (log.isTraceEnabled()) log.trace("Processing saveSerializedView - Checked for duplicate Ids");

         ExternalContext externalContext = facesContext.getExternalContext();

         // SerializedView already created before within this request?

         Object serializedView = externalContext.getRequestMap()

                                                             .get(SERIALIZED_VIEW_REQUEST_ATTR);

         if (serializedView == null)

         {

             if (log.isTraceEnabled()) log.trace("Processing saveSerializedView - create new serialized view");

             // first call to saveSerializedView --> create SerializedView

             Object treeStruct = getTreeStructureToSave(facesContext);

             Object compStates = getComponentStateToSave(facesContext);

             serializedView = new Object[] {treeStruct, compStates};

             externalContext.getRequestMap().put(SERIALIZED_VIEW_REQUEST_ATTR,

                                                 serializedView);

             if (log.isTraceEnabled()) log.trace("Processing saveSerializedView - new serialized view created");

         }

         Object[] serializedViewArray = (Object[]) serializedView;

         if (!isSavingStateInClient(facesContext))

         {

             if (log.isTraceEnabled()) log.trace("Processing saveSerializedView - server-side state saving - save state");

             //save state in server session

             saveSerializedViewInServletSession(facesContext, serializedView);

             if (log.isTraceEnabled()) log.trace("Exiting saveSerializedView - server-side state saving - saved state");

             return new SerializedView(serializedViewArray[0], new Object[0]);

         }

         if (log.isTraceEnabled()) log.trace("Exiting saveSerializedView - client-side state saving");

         return new SerializedView(serializedViewArray[0], serializedViewArray[1]);

     }

     private static void checkForDuplicateIds(FacesContext context,

                                              UIComponent component,

                                              Set<String> ids)

     {

         String id = component.getId();

         if (id != null && !ids.add(id))

         {

             throw new IllegalStateException("Client-id : "+id +

                                             " is duplicated in the faces tree. Component : "+component.getClientId(context)+", path: "+

                                             getPathToComponent(component));

         }

         if (component instanceof NamingContainer)

         {

             ids = new HashSet<String>();

         }

         Iterator it = component.getFacetsAndChildren();

         while (it.hasNext())

         {

             UIComponent kid = (UIComponent) it.next();

             checkForDuplicateIds(context, kid, ids);

         }

     }

     private static String getPathToComponent(UIComponent component)

     {

         StringBuffer buf = new StringBuffer();

         if(component == null)

         {

             buf.append("{Component-Path : ");

             buf.append("[null]}");

             return buf.toString();

         }

         getPathToComponent(component,buf);

         buf.insert(0,"{Component-Path : ");

         buf.append("}");

         return buf.toString();

     }

     private static void getPathToComponent(UIComponent component, StringBuffer buf)

     {

         if(component == null)

             return;

         StringBuffer intBuf = new StringBuffer();

         intBuf.append("[Class: ");

         intBuf.append(component.getClass().getName());

         if(component instanceof UIViewRoot)

         {

             intBuf.append(",ViewId: ");

             intBuf.append(((UIViewRoot) component).getViewId());

         }

         else

         {

             intBuf.append(",Id: ");

             intBuf.append(component.getId());

         }

         intBuf.append("]");

         buf.insert(0,intBuf.toString());

         if(component!=null)

         {

             getPathToComponent(component.getParent(),buf);

         }

     }

     public void writeState(FacesContext facesContext,

                            SerializedView serializedView) throws IOException

     {

         if (log.isTraceEnabled()) log.trace("Entering writeState");

         UIViewRoot uiViewRoot = facesContext.getViewRoot();

         //save state in response (client)

         RenderKit renderKit = getRenderKitFactory().getRenderKit(facesContext, uiViewRoot.getRenderKitId());

         ResponseStateManager responseStateManager = renderKit.getResponseStateManager();

         if (isLegacyResponseStateManager(responseStateManager))

         {

             responseStateManager.writeState(facesContext, serializedView);

         }

         else if (!isSavingStateInClient(facesContext))

         {

             Object[] state = new Object[2];

             state[JSF_SEQUENCE_INDEX] = Integer.toString(getNextViewSequence(facesContext), Character.MAX_RADIX);

             responseStateManager.writeState(facesContext, state);

         }

         else

         {

             Object[] state = new Object[2];

             state[0] = serializedView.getStructure();

             state[1] = serializedView.getState();

             responseStateManager.writeState(facesContext, state);

         }

         if (log.isTraceEnabled()) log.trace("Exiting writeState");

     }

     /**

      * MyFaces extension

      * @param facesContext

      * @param serializedView

      * @throws IOException

      */

     public void writeStateAsUrlParams(FacesContext facesContext,

                                       SerializedView serializedView) throws IOException

     {

         if (log.isTraceEnabled()) log.trace("Entering writeStateAsUrlParams");

         if (isSavingStateInClient(facesContext))

         {

             if (log.isTraceEnabled()) log.trace("Processing writeStateAsUrlParams - client-side state saving writing state");

             UIViewRoot uiViewRoot = facesContext.getViewRoot();

             //save state in response (client)

             RenderKit renderKit = getRenderKitFactory().getRenderKit(facesContext, uiViewRoot.getRenderKitId());

             ResponseStateManager responseStateManager = renderKit.getResponseStateManager();

             if (responseStateManager instanceof MyfacesResponseStateManager)

             {

                 ((MyfacesResponseStateManager)responseStateManager).writeStateAsUrlParams(facesContext,

                                                                                           serializedView);

             }

             else

             {

                 log.error("ResponseStateManager of render kit " + uiViewRoot.getRenderKitId() + " is no MyfacesResponseStateManager and does not support saving state in url parameters.");

             }

         }

         if (log.isTraceEnabled()) log.trace("Exiting writeStateAsUrlParams");

     }

     //helpers

     protected RenderKitFactory getRenderKitFactory()

     {

         if (_renderKitFactory == null)

         {

             _renderKitFactory = (RenderKitFactory)FactoryFinder.getFactory(FactoryFinder.RENDER_KIT_FACTORY);

         }

         return _renderKitFactory;

     }

     protected void saveSerializedViewInServletSession(FacesContext context,

                                                       Object serializedView)

     {

         Map<String, Object> sessionMap = context.getExternalContext().getSessionMap();

         SerializedViewCollection viewCollection = (SerializedViewCollection) sessionMap

                 .get(SERIALIZED_VIEW_SESSION_ATTR);

         if (viewCollection == null)

         {

             viewCollection = new SerializedViewCollection();

             sessionMap.put(SERIALIZED_VIEW_SESSION_ATTR, viewCollection);

         }

         viewCollection.add(context, serializeView(context, serializedView));

         // replace the value to notify the container about the change

         sessionMap.put(SERIALIZED_VIEW_SESSION_ATTR, viewCollection);

     }

     protected Object getSerializedViewFromServletSession(FacesContext context, String viewId, Integer sequence)

     {

         ExternalContext externalContext = context.getExternalContext();

         Map<String, Object> requestMap = externalContext.getRequestMap();

         Object serializedView = null;

         if (requestMap.containsKey(RESTORED_SERIALIZED_VIEW_REQUEST_ATTR))

         {

             serializedView = requestMap.get(RESTORED_SERIALIZED_VIEW_REQUEST_ATTR);

         }

         else

         {

             SerializedViewCollection viewCollection = (SerializedViewCollection) externalContext

                     .getSessionMap().get(SERIALIZED_VIEW_SESSION_ATTR);

             if (viewCollection != null)

             {

                 /*

                 String sequenceStr = externalContext.getRequestParameterMap().get(

                        RendererUtils.SEQUENCE_PARAM);

                 Integer sequence = null;

                 if (sequenceStr == null)

                 {

                     // use latest sequence

                     Map map = externalContext.getSessionMap();

                     sequence = (Integer) map.get(RendererUtils.SEQUENCE_PARAM);

                 }

                 else

                 {

                     sequence = new Integer(sequenceStr);

                 }

                 */

                 if (sequence != null)

                 {

                     Object state = viewCollection.get(sequence, viewId);

                     if (state != null)

                     {

                         serializedView = deserializeView(state);

                     }

                 }

             }

             requestMap.put(RESTORED_SERIALIZED_VIEW_REQUEST_ATTR, serializedView);

             nextViewSequence(context);

         }

         return serializedView;

     }

     protected int getNextViewSequence(FacesContext context)

     {

         ExternalContext externalContext = context.getExternalContext();

         if (!externalContext.getRequestMap().containsKey(RendererUtils.SEQUENCE_PARAM))

         {

             nextViewSequence(context);

         }

         Integer sequence = (Integer) externalContext.getRequestMap().get(RendererUtils.SEQUENCE_PARAM);

         return sequence.intValue();

     }

     protected void nextViewSequence(FacesContext facescontext)

     {

         ExternalContext externalContext = facescontext.getExternalContext();

         Object sessionObj = externalContext.getSession(true);

         synchronized(sessionObj) // synchronized to increase sequence if multiple requests

                                  // are handled at the same time for the session

         {

             Map<String, Object> map = externalContext.getSessionMap();

             Integer sequence = (Integer) map.get(RendererUtils.SEQUENCE_PARAM);

             if(sequence == null || sequence.intValue() == Integer.MAX_VALUE)

             {

                 sequence = Integer.valueOf(1);

             }

             else

             {

                 sequence = Integer.valueOf(sequence.intValue() + 1);

             }

             map.put(RendererUtils.SEQUENCE_PARAM, sequence);

             externalContext.getRequestMap().put(RendererUtils.SEQUENCE_PARAM, sequence);

         }

     }

     protected Object serializeView(FacesContext context, Object serializedView)

     {

         if (log.isTraceEnabled()) log.trace("Entering serializeView");

         if(isSerializeStateInSession(context))

         {

             if (log.isTraceEnabled()) log.trace("Processing serializeView - serialize state in session");

             ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);

             try

             {

                 OutputStream os = baos;

                 if(isCompressStateInSession(context))

                 {

                     if (log.isTraceEnabled()) log.trace("Processing serializeView - serialize compressed");

                     os.write(COMPRESSED_FLAG);

                     os = new GZIPOutputStream(os, 1024);

                 }

                 else

                 {

                     if (log.isTraceEnabled()) log.trace("Processing serializeView - serialize uncompressed");

                     os.write(UNCOMPRESSED_FLAG);

                 }

                 Object[] stateArray = (Object[]) serializedView;

                 ObjectOutputStream out = new ObjectOutputStream(os);

                 out.writeObject(stateArray[0]);

                 out.writeObject(stateArray[1]);

                 out.close();

                 baos.close();

                 if (log.isTraceEnabled()) log.trace("Exiting serializeView - serialized. Bytes : "+baos.size());

                 return baos.toByteArray();

             }

             catch (IOException e)

             {

                 log.error("Exiting serializeView - Could not serialize state: " + e.getMessage(), e);

                 return null;

             }

         }

         if (log.isTraceEnabled())

             log.trace("Exiting serializeView - do not serialize state in session.");

         return serializedView;

     }

     /**

      * Reads the value of the <code>org.apache.myfaces.SERIALIZE_STATE_IN_SESSION</code> context parameter.

      * @see SERIALIZE_STATE_IN_SESSION_PARAM

      * @param context <code>FacesContext</code> for the request we are processing.

      * @return boolean true, if the server state should be serialized in the session

      */

     protected boolean isSerializeStateInSession(FacesContext context)

     {

         String value = context.getExternalContext().getInitParameter(

                 SERIALIZE_STATE_IN_SESSION_PARAM);

         boolean serialize = DEFAULT_SERIALIZE_STATE_IN_SESSION;

         if (value != null)

         {

            serialize = Boolean.valueOf(value);

         }

         return serialize;

     }

     /**

      * Reads the value of the <code>org.apache.myfaces.COMPRESS_STATE_IN_SESSION</code> context parameter.

      * @see COMPRESS_SERVER_STATE_PARAM

      * @param context <code>FacesContext</code> for the request we are processing.

      * @return boolean true, if the server state steam should be compressed

      */

     protected boolean isCompressStateInSession(FacesContext context)

     {

         String value = context.getExternalContext().getInitParameter(

                 COMPRESS_SERVER_STATE_PARAM);

         boolean compress = DEFAULT_COMPRESS_SERVER_STATE_PARAM;

         if (value != null)

         {

            compress = Boolean.valueOf(value);

         }

         return compress;

     }

     protected Object deserializeView(Object state)

     {

         if (log.isTraceEnabled()) log.trace("Entering deserializeView");

         if(state instanceof byte[])

         {

             if (log.isTraceEnabled()) log.trace("Processing deserializeView - deserializing serialized state. Bytes : "+((byte[]) state).length);

             try

             {

                 ByteArrayInputStream bais = new ByteArrayInputStream((byte[]) state);

                 InputStream is = bais;

                 if(is.read() == COMPRESSED_FLAG)

                 {

                     is = new GZIPInputStream(is);

                 }

                 ObjectInputStream ois = null;

                 try

                 {

                     final ObjectInputStream in = new MyFacesObjectInputStream(is);

                     ois = in;

                     Object object = null;

                     if (System.getSecurityManager() != null) 

                     {

                         object = AccessController.doPrivileged(new PrivilegedExceptionAction<Object []>() 

                         {

                             public Object[] run() throws PrivilegedActionException, IOException, ClassNotFoundException

                             {

                                 return new Object[] {in.readObject(), in.readObject()};                                    

                             }

                         });

                     }

                     else

                     {

                         object = new Object[] {in.readObject(), in.readObject()};

                     }

                     return object;

                 }

                 finally

                 {

                     if (ois != null)

                     {

                         ois.close();

                         ois = null;

                     }

                 }

             }

             catch (PrivilegedActionException e) 

             {

                 log.error("Exiting deserializeView - Could not deserialize state: " + e.getMessage(), e);

                 return null;

             }

             catch (IOException e)

             {

                 log.error("Exiting deserializeView - Could not deserialize state: " + e.getMessage(), e);

                 return null;

             }

             catch (ClassNotFoundException e)

             {

                 log.error("Exiting deserializeView - Could not deserialize state: " + e.getMessage(), e);

                 return null;

             }

         }

         else if (state instanceof Object[])

         {

             if (log.isTraceEnabled()) log.trace("Exiting deserializeView - state not serialized.");

             return state;

         }

         else if(state == null)

         {

             log.error("Exiting deserializeView - this method should not be called with a null-state.");

             return null;

         }

         else

         {

             log.error("Exiting deserializeView - this method should not be called with a state of type : "+state.getClass());

             return null;

         }

     }

     private boolean isLegacyResponseStateManager(ResponseStateManager instance) {

         Method[] methods = instance.getClass().getMethods();

         for (Method m : methods)

         {

             if (m.getName().equals("getState") &&

                     Arrays.equals(m.getParameterTypes(),new Class[] {FacesContext.class, String.class}))

             {

                  return false;

             }

         }

         return true;

     }

     protected static class SerializedViewCollection implements Serializable

     {

         private static final long serialVersionUID = -3734849062185115847L;

         private final List<Object> _keys = new ArrayList<Object>(DEFAULT_NUMBER_OF_VIEWS_IN_SESSION);

         private final Map<Object, Object> _serializedViews = new HashMap<Object, Object>();

         // old views will be hold as soft references which will be removed by

         // the garbage collector if free memory is low

         private transient Map<Object, Object> _oldSerializedViews = null;

         public synchronized void add(FacesContext context, Object state)

         {

             Object key = new SerializedViewKey(context);

             _serializedViews.put(key, state);

             while (_keys.remove(key));

             _keys.add(key);

             int views = getNumberOfViewsInSession(context);

             while (_keys.size() > views)

             {

                 key = _keys.remove(0);

                 Object oldView = _serializedViews.remove(key);

                 if (oldView != null && 

                     !CACHE_OLD_VIEWS_IN_SESSION_MODE_OFF.equals(getCacheOldViewsInSessionMode(context))) 

                 {

                     getOldSerializedViewsMap().put(key, oldView);

                 }

             }

         }

         /**

          * Reads the amount (default = 20) of views to be stored in session.

          * @see NUMBER_OF_VIEWS_IN_SESSION_PARAM

          * @param context FacesContext for the current request, we are processing

          * @return Number vf views stored in the session

          */

         protected int getNumberOfViewsInSession(FacesContext context)

         {

             String value = context.getExternalContext().getInitParameter(

                     NUMBER_OF_VIEWS_IN_SESSION_PARAM);

             int views = DEFAULT_NUMBER_OF_VIEWS_IN_SESSION;

             if (value != null)

             {

                 try

                 {

                     views = Integer.parseInt(value);

                     if (views <= 0)

                     {

                         log.error("Configured value for " + NUMBER_OF_VIEWS_IN_SESSION_PARAM

                                   + " is not valid, must be an value > 0, using default value ("

                                   + DEFAULT_NUMBER_OF_VIEWS_IN_SESSION);

                         views = DEFAULT_NUMBER_OF_VIEWS_IN_SESSION;

                     }

                 }

                 catch (Throwable e)

                 {

                     log.error("Error determining the value for " + NUMBER_OF_VIEWS_IN_SESSION_PARAM

                               + ", expected an integer value > 0, using default value ("

                               + DEFAULT_NUMBER_OF_VIEWS_IN_SESSION + "): " + e.getMessage(), e);

                 }

             }

             return views;

         }

         /**

          * @return old serialized views map

          */

         protected Map<Object, Object> getOldSerializedViewsMap()

         {

             FacesContext context = FacesContext.getCurrentInstance();

             if (_oldSerializedViews == null && context != null)

             {

                 String cacheMode = getCacheOldViewsInSessionMode(context); 

                 if (CACHE_OLD_VIEWS_IN_SESSION_MODE_WEAK.equals(cacheMode))

                 {

                     _oldSerializedViews = new ReferenceMap(AbstractReferenceMap.WEAK, AbstractReferenceMap.WEAK, true);

                 }

                 else if (CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT_WEAK.equals(cacheMode))

                 {

                     _oldSerializedViews = new ReferenceMap(AbstractReferenceMap.SOFT, AbstractReferenceMap.WEAK, true);

                 }

                 else if (CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT.equals(cacheMode))

                 {

                     _oldSerializedViews = new ReferenceMap(AbstractReferenceMap.SOFT, AbstractReferenceMap.SOFT, true);

                 }

                 else if (CACHE_OLD_VIEWS_IN_SESSION_MODE_HARD_SOFT.equals(cacheMode))

                 {

                     _oldSerializedViews = new ReferenceMap(AbstractReferenceMap.HARD, AbstractReferenceMap.SOFT);

                 }

             }

             return _oldSerializedViews;

         }

         /**

          * Reads the value of the <code>org.apache.myfaces.CACHE_OLD_VIEWS_IN_SESSION_MODE</code> context parameter.

          * 

          * @since 1.2.5

          * @param context

          * @return constant indicating caching mode

          * @see CACHE_OLD_VIEWS_IN_SESSION_MODE

          */

         protected String getCacheOldViewsInSessionMode(FacesContext context) {

             String value = context.getExternalContext().getInitParameter(

                     CACHE_OLD_VIEWS_IN_SESSION_MODE);

             if (value == null)

             {

                 return CACHE_OLD_VIEWS_IN_SESSION_MODE_OFF;

             }

             else if (value.equalsIgnoreCase(CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT))

             {

                 return CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT;

             }

             else if (value.equalsIgnoreCase(CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT_WEAK))

             {

                 return CACHE_OLD_VIEWS_IN_SESSION_MODE_SOFT_WEAK;

             }            

             else if (value.equalsIgnoreCase(CACHE_OLD_VIEWS_IN_SESSION_MODE_WEAK))

             {

                 return CACHE_OLD_VIEWS_IN_SESSION_MODE_WEAK;

             }

             else if (value.equalsIgnoreCase(CACHE_OLD_VIEWS_IN_SESSION_MODE_HARD_SOFT))

             {

                 return CACHE_OLD_VIEWS_IN_SESSION_MODE_HARD_SOFT;

             }

             else

             {

                 return CACHE_OLD_VIEWS_IN_SESSION_MODE_OFF;

             }

         }

         public Object get(Integer sequence, String viewId)

         {

             Object key = new SerializedViewKey(viewId, sequence);

             Object value = _serializedViews.get(key);

             if (value == null)

             {

                 Map<Object,Object> oldSerializedViewMap = getOldSerializedViewsMap();

                 if (oldSerializedViewMap != null)

                 {

                     value = oldSerializedViewMap.get(key);

                 }

             }

             return value;

         }

     }

     protected static class SerializedViewKey implements Serializable

     {

         private static final long serialVersionUID = -1170697124386063642L;

         private final String _viewId;

         private final Integer _sequenceId;

         public SerializedViewKey(String viewId, Integer sequence)

         {

             _sequenceId = sequence;

             _viewId = viewId;

         }

         public SerializedViewKey(FacesContext context)

         {

             _sequenceId = RendererUtils.getViewSequence(context);

             _viewId = context.getViewRoot().getViewId();

         }

         @Override

         public int hashCode()

         {

             final int PRIME = 31;

             int result = 1;

             result = PRIME * result + ((_sequenceId == null) ? 0 : _sequenceId.hashCode());

             result = PRIME * result + ((_viewId == null) ? 0 : _viewId.hashCode());

             return result;

         }

         @Override

         public boolean equals(Object obj)

         {

             if (this == obj)

                 return true;

             if (obj == null)

                 return false;

             if (getClass() != obj.getClass())

                 return false;

             final SerializedViewKey other = (SerializedViewKey) obj;

             if (_sequenceId == null)

             {

                 if (other._sequenceId != null)

                     return false;

             }

             else if (!_sequenceId.equals(other._sequenceId))

                 return false;

             if (_viewId == null)

             {

                 if (other._viewId != null)

                     return false;

             }

             else if (!_viewId.equals(other._viewId))

                 return false;

             return true;

         }

     }

 }