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 * @author Howard M. Lewis Ship
019 * @since 4.0
020 */
021public interface ApplicationStateManager
022{
023    /**
024     * Checks to see if the named object exists.
025     * 
026     * @param objectName
027     *            the name of the application state object
028     * @throws org.apache.hivemind.ApplicationRuntimeException
029     *             if no such object is declared
030     */
031    public boolean exists(String objectName);
032
033    /**
034     * Gets the named application state object, creating it if necessary.
035     * 
036     * @param objectName
037     *            the name of the application state object
038     * @return the object
039     * @throws org.apache.hivemind.ApplicationRuntimeException
040     *             if no such object is declared
041     */
042    public Object get(String objectName);
043    
044    /**
045     * Stores a new state object, replacing the old one. The
046     * new object may be null.
047     * 
048     * @param objectName the name of the object to store
049     * @param stateObject the new object, possibly null
050     * @throws org.apache.hivemind.ApplicationRuntimeException
051     *             if no such object is declared
052     */
053    
054    public void store(String objectName, Object stateObject);
055
056    /**
057     * Asks each {@link StateObjectManager} to store each object obtained.
058     */
059
060    public void flush();
061}