// Copyright 2005 Howard M. Lewis Ship

 //

 // Licensed 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 com.javaforge.tapestry.flash;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.Collections;

 import org.apache.hivemind.util.Defense;

 import org.apache.tapestry.engine.ServiceEncoding;

 import org.apache.tapestry.record.PropertyChange;

 import org.apache.tapestry.record.PropertyPersistenceStrategy;

 import org.apache.tapestry.record.RecordUtils;

 import org.apache.tapestry.record.WebSessionAttributeCallback;

 import org.apache.tapestry.web.WebRequest;

 import org.apache.tapestry.web.WebSession;

 /**

  * A variation of {@link org.apache.tapestry.record.SessionPropertyPersistenceStrategy} where values

  * are stored in the session just until used to rewind a page's state, at which point they are

  * removed. This concept is borrowed from Ruby-On-Rails, in effect.

  * 

  * @author Howard M. Lewis Ship

  */

 public class FlashPropertyPersistenceStrategy implements PropertyPersistenceStrategy

 {

     public static final String STRATEGY_ID = "flash";

     // Really, the name of the servlet; used as a prefix on all HttpSessionAttribute keys

     // to keep things straight if multiple Tapestry apps are deployed

     // in the same WAR.

     private String _applicationId;

     private WebRequest _request;

     public void store(String pageName, String idPath, String propertyName, Object newValue)

     {

         Defense.notNull(pageName, "pageName");

         Defense.notNull(propertyName, "propertyName");

         WebSession session = _request.getSession(true);

         String attributeName = RecordUtils.buildChangeKey(

                 STRATEGY_ID,

                 _applicationId,

                 pageName,

                 idPath,

                 propertyName);

         session.setAttribute(attributeName, newValue);

     }

     public Collection getStoredChanges(String pageName)

     {

         Defense.notNull(pageName, "pageName");

         WebSession session = _request.getSession(false);

         if (session == null)

             return Collections.EMPTY_LIST;

         final Collection result = new ArrayList();

         WebSessionAttributeCallback callback = new WebSessionAttributeCallback()

         {

             public void handleAttribute(WebSession session, String name)

             {

                 PropertyChange change = RecordUtils.buildChange(name, session.getAttribute(name));

                 result.add(change);

                 // The only significant change between SessionPropertyPersistenceStorage and this

                 // class as we retrieve PropertyChanges to be used to rollback page state, we remove

                 // those changes from the WebSession

                 session.setAttribute(name, null);

             }

         };

         RecordUtils.iterateOverMatchingAttributes(

                 STRATEGY_ID,

                 _applicationId,

                 pageName,

                 session,

                 callback);

         return result;

     }

     public void discardStoredChanges(String pageName)

     {

         WebSession session = _request.getSession(false);

         if (session == null)

             return;

         WebSessionAttributeCallback callback = new WebSessionAttributeCallback()

         {

             public void handleAttribute(WebSession session, String name)

             {

                 session.setAttribute(name, null);

             }

         };

         RecordUtils.iterateOverMatchingAttributes(

                 STRATEGY_ID,

                 _applicationId,

                 pageName,

                 session,

                 callback);

     }

     /**

      * Does nothing; session persistence does not make use of query parameters.

      */

     public void addParametersForPersistentProperties(ServiceEncoding encoding, boolean post)

     {

     }

     public void setApplicationId(String applicationName)

     {

         _applicationId = applicationName;

     }

     public void setRequest(WebRequest request)

     {

         _request = request;

     }

 }