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.codec.demux;
021
022import org.apache.mina.core.buffer.IoBuffer;
023import org.apache.mina.core.session.IoSession;
024import org.apache.mina.filter.codec.ProtocolEncoderOutput;
025
026/**
027 * Encodes a certain type of messages.
028 * <p>
029 * We didn't provide any <tt>dispose</tt> method for {@link MessageEncoder}
030 * because it can give you  performance penalty in case you have a lot of
031 * message types to handle.
032 * 
033 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
034 *
035 * @see DemuxingProtocolEncoder
036 * @see MessageEncoderFactory
037 * 
038 * @param T The message type
039 */
040public interface MessageEncoder<T> {
041    /**
042     * Encodes higher-level message objects into binary or protocol-specific data.
043     * MINA invokes {@link #encode(IoSession, Object, ProtocolEncoderOutput)}
044     * method with message which is popped from the session write queue, and then
045     * the encoder implementation puts encoded {@link IoBuffer}s into
046     * {@link ProtocolEncoderOutput}.
047     *
048     * @param session The current session 
049     * @param message The message to encode
050     * @param out The instance of {@link ProtocolEncoderOutput} that will receive the encoded message
051     * @throws Exception if the message violated protocol specification
052     */
053    void encode(IoSession session, T message, ProtocolEncoderOutput out) throws Exception;
054}