001    // Copyright 2005 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    //     http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry.engine.state;
016    
017    import org.apache.tapestry.SessionStoreOptimized;
018    import org.apache.tapestry.web.WebRequest;
019    import org.apache.tapestry.web.WebSession;
020    
021    /**
022     * Manager for the 'session' scope; state objects are stored as HttpSession attributes. The
023     * HttpSession is created as necessary.
024     * 
025     * @author Howard M. Lewis Ship
026     * @since 4.0
027     */
028    public class SessionScopeManager implements StateObjectPersistenceManager
029    {
030        private WebRequest _request;
031    
032        private String _applicationId;
033    
034        private String buildKey(String objectName)
035        {
036            // For Portlets, the application id is going to be somewhat redundant, since
037            // the Portlet API keeps portlets seperate anyway.
038    
039            return "state:" + _applicationId + ":" + objectName;
040        }
041    
042        /**
043         * Returns the session for the current request, creating it if necessary.
044         */
045    
046        private WebSession getSession()
047        {
048            return _request.getSession(true);
049        }
050    
051        public boolean exists(String objectName)
052        {
053            WebSession session = _request.getSession(false);
054    
055            if (session == null)
056                return false;
057    
058            return session.getAttribute(buildKey(objectName)) != null;
059        }
060    
061        public Object get(String objectName, StateObjectFactory factory)
062        {
063            String key = buildKey(objectName);
064            WebSession session = getSession();
065    
066            Object result = session.getAttribute(key);
067            if (result == null)
068            {
069                result = factory.createStateObject();
070                session.setAttribute(key, result);
071            }
072    
073            return result;
074        }
075    
076        public void store(String objectName, Object stateObject)
077        {
078            if (stateObject instanceof SessionStoreOptimized)
079            {
080                SessionStoreOptimized optimized = (SessionStoreOptimized) stateObject;
081    
082                if (!optimized.isStoreToSessionNeeded())
083                    return;
084            }
085    
086            String key = buildKey(objectName);
087    
088            WebSession session = getSession();
089    
090            session.setAttribute(key, stateObject);
091        }
092    
093        public void setApplicationId(String applicationName)
094        {
095            _applicationId = applicationName;
096        }
097    
098        public void setRequest(WebRequest request)
099        {
100            _request = request;
101        }
102    }