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    
015    package org.apache.tapestry.engine.state;
016    
017    /**
018     * @author Howard M. Lewis Ship
019     * @since 4.0
020     */
021    public 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    }