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.util;
021
022import org.apache.mina.core.filterchain.IoFilter;
023import org.apache.mina.core.filterchain.IoFilterAdapter;
024import org.apache.mina.core.session.IoEventType;
025import org.apache.mina.core.session.IoSession;
026import org.apache.mina.core.write.WriteRequest;
027import org.apache.mina.core.write.WriteRequestWrapper;
028
029/**
030 * An abstract {@link IoFilter} that simplifies the implementation of
031 * an {@link IoFilter} that filters an {@link IoEventType#WRITE} event.
032 *
033 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
034 *
035 */
036public abstract class WriteRequestFilter extends IoFilterAdapter {
037    @Override
038    public void filterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
039        Object filteredMessage = doFilterWrite(nextFilter, session, writeRequest);
040        if (filteredMessage != null && filteredMessage != writeRequest.getMessage()) {
041            nextFilter.filterWrite(session, new FilteredWriteRequest(filteredMessage, writeRequest));
042        } else {
043            nextFilter.filterWrite(session, writeRequest);
044        }
045    }
046
047    @Override
048    public void messageSent(NextFilter nextFilter, IoSession session, WriteRequest writeRequest) throws Exception {
049        if (writeRequest instanceof FilteredWriteRequest) {
050            FilteredWriteRequest req = (FilteredWriteRequest) writeRequest;
051            if (req.getParent() == this) {
052                nextFilter.messageSent(session, req.getParentRequest());
053                return;
054            }
055        }
056
057        nextFilter.messageSent(session, writeRequest);
058    }
059
060    protected abstract Object doFilterWrite(NextFilter nextFilter, IoSession session, WriteRequest writeRequest)
061            throws Exception;
062
063    private class FilteredWriteRequest extends WriteRequestWrapper {
064        private final Object filteredMessage;
065
066        public FilteredWriteRequest(Object filteredMessage, WriteRequest writeRequest) {
067            super(writeRequest);
068
069            if (filteredMessage == null) {
070                throw new IllegalArgumentException("filteredMessage");
071            }
072            this.filteredMessage = filteredMessage;
073        }
074
075        public WriteRequestFilter getParent() {
076            return WriteRequestFilter.this;
077        }
078
079        @Override
080        public Object getMessage() {
081            return filteredMessage;
082        }
083    }
084}