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
015package org.apache.tapestry5.services;
016
017import 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)
035public 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}