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;
016    
017    import java.io.Serializable;
018    
019    import javax.servlet.http.HttpSessionBindingEvent;
020    import javax.servlet.http.HttpSessionBindingListener;
021    
022    /**
023     * Base implementation of {@link org.apache.tapestry.SessionStoreOptimized}. Subclasses should
024     * invoke {@link #markSessionStoreNeeded()} any time internal state changed.
025     * 
026     * @author Howard M. Lewis Ship
027     * @since 4.0
028     */
029    public class BaseSessionStoreOptimized implements SessionStoreOptimized, Serializable,
030            HttpSessionBindingListener
031    {
032        private static final long serialVersionUID = -2786704444616789831L;
033    
034        private transient boolean _dirty;
035    
036        /**
037         * Clears the dirty flag.
038         */
039        public void valueBound(HttpSessionBindingEvent event)
040        {
041            _dirty = false;
042        }
043    
044        /**
045         * Does nothing.
046         */
047        public void valueUnbound(HttpSessionBindingEvent event)
048        {
049        }
050    
051        /**
052         * Sets the dirty flag.
053         */
054        protected void markSessionStoreNeeded()
055        {
056            _dirty = true;
057        }
058    
059        /**
060         * Returns the dirty flag.
061         */
062        public boolean isStoreToSessionNeeded()
063        {
064            return _dirty;
065        }
066    
067    }