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.engine.state; 016 017/** 018 * Interface for an object that manages a single application state object. Represents the named 019 * intersection of a {@link org.apache.tapestry.engine.state.StateObjectPersistenceManager}for 020 * storing the state object between request cycles, and a 021 * {@link org.apache.tapestry.engine.state.StateObjectFactory}to create the object in the first 022 * place. 023 * 024 * @author Howard M. Lewis Ship 025 * @since 4.0 026 */ 027public interface StateObjectManager 028{ 029 /** 030 * Returns true if the application state object exists (i.e., a value has been stored). 031 */ 032 public boolean exists(); 033 034 /** 035 * Gets or creates the application state object. 036 */ 037 038 public Object get(); 039 040 /** 041 * Stores (if necessary) the object back into persistent storage. This is not application to all 042 * storage scopes. 043 * 044 * @param stateObject 045 * the application state object previously obtained from {@link #get()}. 046 */ 047 048 public void store(Object stateObject); 049}