001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 *
019 */
020package org.apache.mina.filter.executor;
021
022import java.util.EventListener;
023
024import org.apache.mina.core.session.IoEvent;
025
026/**
027 * Listens and filters all event queue operations occurring in
028 * {@link OrderedThreadPoolExecutor} and {@link UnorderedThreadPoolExecutor}.
029 *
030 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
031 */
032public interface IoEventQueueHandler extends EventListener {
033
034    /**
035     * A dummy handler which always accepts event doing nothing particular.
036     */
037    IoEventQueueHandler NOOP = new IoEventQueueHandler() {
038        public boolean accept(Object source, IoEvent event) {
039            return true;
040        }
041
042        public void offered(Object source, IoEvent event) {
043            // NOOP
044        }
045
046        public void polled(Object source, IoEvent event) {
047            // NOOP
048        }
049    };
050
051    /**
052     * @return <tt>true</tt> if and only if the specified <tt>event</tt> is
053     * allowed to be offered to the event queue.  The <tt>event</tt> is dropped
054     * if <tt>false</tt> is returned.
055     * 
056     * @param source The source of event
057     * @param event The received event
058     */
059    boolean accept(Object source, IoEvent event);
060
061    /**
062     * Invoked after the specified <tt>event</tt> has been offered to the
063     * event queue.
064     * 
065     * @param source The source of event
066     * @param event The received event
067     */
068    void offered(Object source, IoEvent event);
069
070    /**
071     * Invoked after the specified <tt>event</tt> has been polled from the
072     * event queue.
073     * 
074     * @param source The source of event
075     * @param event The received event
076     */
077    void polled(Object source, IoEvent event);
078}