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    
015    package org.apache.hivemind.events;
016    
017    import 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     */
042    public 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    }