001// Copyright 2004, 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.services;
016
017import org.apache.tapestry.IEngine;
018
019/**
020 * Service responsible for obtaining instances of {@link org.apache.tapestry.IEngine}
021 * to service the current request.  An engine service may be retrieved from a pool, or extracted
022 * from the HttpSession. After the request is processed, the engine is re-stored into the
023 * HttpSession (if stateful) or back into the pool (if not stateful).
024 *
025 * @author Howard Lewis Ship
026 * @since 4.0
027 */
028public interface EngineManager
029{
030        /**
031         * Locates or creates an engine instance for the current request.
032         */
033        IEngine getEngineInstance();
034        
035        /**
036         * Store the engine back at the end of the current request.
037         */
038        
039        void storeEngineInstance(IEngine engine);
040}