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.service;
016    
017    /**
018     * Service which acts as a dispatch hub for events about the lifecycle of the current thread.
019     * <p>
020     * Note: prior to release 1.1.1, the ThreadEventNotifier implementation would retain the listeners
021     * after {@link #fireThreadCleanup()}, which could allow certain threads to retain a reference to a
022     * listener, and thus that listener's class loader, even after the an application redeployment,
023     * resulting in a massive memory leak. Starting with release 1.1.1, all listeners are discarded by
024     * {@link #fireThreadCleanup()}.
025     * 
026     * @author Howard Lewis Ship
027     */
028    public interface ThreadEventNotifier
029    {
030        /**
031         * Adds the listener. The notifier retains the listener until {@link #fireThreadCleanup()} is
032         * invoked, at which point is discarded.
033         */
034        public void addThreadCleanupListener(ThreadCleanupListener listener);
035    
036        /**
037         * Removes the listener, if it has been previously added. If the listener has been added
038         * multiple times, only one instance is removed. Note that this method is rarely used, because
039         * all listeners are automatically removed by {@link #fireThreadCleanup()}.
040         */
041        public void removeThreadCleanupListener(ThreadCleanupListener listener);
042    
043        /**
044         * Invokes {@link ThreadCleanupListener#threadDidCleanup()} on all listeners, and discards the
045         * list of listeners.
046         */
047        public void fireThreadCleanup();
048    }