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1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one
3    *  or more contributor license agreements.  See the NOTICE file
4    *  distributed with this work for additional information
5    *  regarding copyright ownership.  The ASF licenses this file
6    *  to you under the Apache License, Version 2.0 (the
7    *  "License"); you may not use this file except in compliance
8    *  with the License.  You may obtain a copy of the License at
9    *  
10   *    http://www.apache.org/licenses/LICENSE-2.0
11   *  
12   *  Unless required by applicable law or agreed to in writing,
13   *  software distributed under the License is distributed on an
14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   *  KIND, either express or implied.  See the License for the
16   *  specific language governing permissions and limitations
17   *  under the License. 
18   *  
19   */
20  package org.apache.mina.example.sumup.codec;
21  
22  import org.apache.mina.common.ByteBuffer;
23  import org.apache.mina.common.IoSession;
24  import org.apache.mina.example.sumup.message.AbstractMessage;
25  import org.apache.mina.filter.codec.ProtocolEncoderOutput;
26  import org.apache.mina.filter.codec.demux.MessageEncoder;
27  
28  /**
29   * A {@link MessageEncoder} that encodes message header and forwards
30   * the encoding of body to a subclass.
31   *
32   * @author The Apache Directory Project (mina-dev@directory.apache.org)
33   * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (금, 13  7월 2007) $
34   */
35  public abstract class AbstractMessageEncoder implements MessageEncoder {
36      private final int type;
37  
38      protected AbstractMessageEncoder(int type) {
39          this.type = type;
40      }
41  
42      public void encode(IoSession session, Object message,
43              ProtocolEncoderOutput out) throws Exception {
44          AbstractMessage m = (AbstractMessage) message;
45          ByteBuffer buf = ByteBuffer.allocate(16);
46          buf.setAutoExpand(true); // Enable auto-expand for easier encoding
47  
48          // Encode a header
49          buf.putShort((short) type);
50          buf.putInt(m.getSequence());
51  
52          // Encode a body
53          encodeBody(session, m, buf);
54          buf.flip();
55          out.write(buf);
56      }
57  
58      protected abstract void encodeBody(IoSession session,
59              AbstractMessage message, ByteBuffer out);
60  }