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; 016 017/** 018 * <em>Optional</em> interface implemented by Application State Objects. This interface allows 019 * Tapestry to optimize the storage of the objects into the 020 * {@link org.apache.tapestry.web.WebSession session}, only storing the objects when they require 021 * storage due to a change in internal state. 022 * 023 * @author Howard M. Lewis Ship 024 * @since 4.0 025 */ 026public interface SessionStoreOptimized 027{ 028 /** 029 * Queried by the {@link org.apache.tapestry.engine.state.StateObjectManager} to see if the 030 * object actually needs to be stored. Objects that implement this interface should store an 031 * internal flag. The flag should be set when any change to the object's internal state occurs. 032 * The flag should be cleared when the object is stored into the session (typically, by 033 * implementing {@link javax.servlet.http.HttpSessionBindingListener}. 034 * 035 * @return true if the object needs to be stored back into the session, false if the internal 036 * state of the object is unchanged 037 */ 038 boolean isStoreToSessionNeeded(); 039 040}