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.example.sumup.codec;
021
022import org.apache.mina.core.buffer.IoBuffer;
023import org.apache.mina.core.session.IoSession;
024import org.apache.mina.example.sumup.message.AbstractMessage;
025import org.apache.mina.filter.codec.ProtocolEncoderOutput;
026import org.apache.mina.filter.codec.demux.MessageEncoder;
027
028/**
029 * A {@link MessageEncoder} that encodes message header and forwards
030 * the encoding of body to a subclass.
031 *
032 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
033 */
034public abstract class AbstractMessageEncoder<T extends AbstractMessage> implements MessageEncoder<T> {
035    private final int type;
036
037    protected AbstractMessageEncoder(int type) {
038        this.type = type;
039    }
040
041    public void encode(IoSession session, T message, ProtocolEncoderOutput out) throws Exception {
042        IoBuffer buf = IoBuffer.allocate(16);
043        buf.setAutoExpand(true); // Enable auto-expand for easier encoding
044
045        // Encode a header
046        buf.putShort((short) type);
047        buf.putInt(message.getSequence());
048
049        // Encode a body
050        encodeBody(session, message, buf);
051        buf.flip();
052        out.write(buf);
053    }
054
055    protected abstract void encodeBody(IoSession session, T message, IoBuffer out);
056}