001    // Copyright 2008, 2009, 2011 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.tapestry5;
016    
017    import java.util.concurrent.atomic.AtomicBoolean;
018    
019    /**
020     * Base implementation of
021     * {@link org.apache.tapestry5.OptimizedSessionPersistedObject}. Subclasses
022     * should invoke {@link #markDirty()} after the internal state of the object changes.
023     * <p>
024     * Due to the concurrent nature of session attributes it's important that markDirty occurs <strong>after</strong>
025     * the object has been changed. If the change occurs before the object has been mutated it's possible that another
026     * thread may re-store the object before the changes are actually made!
027     * <p>
028     * @since 5.1.1.0
029     */
030    public abstract class BaseOptimizedSessionPersistedObject implements OptimizedSessionPersistedObject
031    {
032        private transient AtomicBoolean dirty = new AtomicBoolean(false);
033    
034        public final boolean checkAndResetDirtyMarker()
035        {
036            return dirty.getAndSet(false);
037        }
038    
039        /**
040         * Invoked by the subclass after internal state of the object changes.
041         */
042        protected final void markDirty()
043        {
044            dirty.set(true);
045        }
046    }