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
015package org.apache.tapestry.engine.state;
016
017import org.apache.tapestry.SessionStoreOptimized;
018import org.apache.tapestry.web.WebRequest;
019import 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 */
028public 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}