001    // Copyright 2008, 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.services;
016    
017    import org.apache.tapestry5.ioc.annotations.UsesMappedConfiguration;
018    
019    /**
020     * Analyzes a session-persisted object, specifically to see if it is dirty or not.
021     * <p/>
022     * This service is provided to support applications which store mutable session attributes where the
023     * session is replicated to a slower medium (e.g. RDMBS, Cluster, etc) this can help alleviate excessive writes
024     * to the session store while ensuring changes are propagated.
025     * <p/>
026     * The service implementation uses a mapped configuration to form a
027     * {@linkplain org.apache.tapestry5.ioc.services.StrategyBuilder strategy} based on object type. The service may be
028     * injected using the {@link org.apache.tapestry5.ioc.annotations.Primary} marker annotation.
029     *
030     * @see org.apache.tapestry5.annotations.ImmutableSessionPersistedObject
031     * @see org.apache.tapestry5.OptimizedSessionPersistedObject
032     * @since 5.1.0.0
033     */
034    @UsesMappedConfiguration(key = Class.class, value = SessionPersistedObjectAnalyzer.class)
035    public interface SessionPersistedObjectAnalyzer<T>
036    {
037        /**
038         * Atomically check and reset the dirty state of the session persisted object.
039         * <p/>
040         * The implementer should take consideration for the fact that session attributes are accessed concurrently. A
041         * naive check/set algorithm may allow changes to go un-noticed.
042         *
043         * @param sessionPersistedObject the session attribute (never null)
044         * @return true if the object needs to be re-stored into the session
045         * @since 5.3
046         */
047        boolean checkAndResetDirtyState(T sessionPersistedObject);
048    
049    }