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.hivemind.events;
016
017import java.util.EventListener;
018
019/**
020 * Lifecycle interface that may be implemented by objects
021 * that need to know when the {@link org.apache.hivemind.Registry}
022 * has shutdown.  Typically, this is implemented by core service implementations
023 * (as well as many proxies created by HiveMind).
024 * 
025 * <p>
026 * A core service implementation that implements this interface will
027 * automatically be registered for notifications (exception: not if the service
028 * uses the threaded service model).
029 * 
030 * <p>Using this notification is
031 * preferrable to implementing a <code>finalize()</code> since it will be invoked
032 * at a known time.
033 * 
034 * <p>
035 * The order in which listeners will be invoked is
036 * not well known. In the future, some form of dependency system may
037 * be instituted.
038 * 
039 *
040 * @author Howard Lewis Ship
041 */
042public interface RegistryShutdownListener extends EventListener
043{
044        /**
045         * Invoked when a service is being shutdown, and should release any external resources.
046         * A service should <em>not</em> attempt to use any resources or configurations, doing
047         * so may result in a runtime exception.
048         */
049        public void registryDidShutdown();
050}