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1   /*
2    *   @(#) $Id: AbstractMessageEncoder.java 332218 2005-11-10 03:52:42Z trustin $
3    *
4    *   Copyright 2004 The Apache Software Foundation
5    *
6    *   Licensed under the Apache License, Version 2.0 (the "License");
7    *   you may not use this file except in compliance with the License.
8    *   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, software
13   *   distributed under the License is distributed on an "AS IS" BASIS,
14   *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   *   See the License for the specific language governing permissions and
16   *   limitations under the License.
17   *
18   */
19  package org.apache.mina.examples.sumup.codec;
20  
21  import org.apache.mina.common.ByteBuffer;
22  import org.apache.mina.examples.sumup.message.AbstractMessage;
23  import org.apache.mina.protocol.ProtocolEncoderOutput;
24  import org.apache.mina.protocol.ProtocolSession;
25  import org.apache.mina.protocol.ProtocolViolationException;
26  import org.apache.mina.protocol.codec.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
33   * @version $Rev: 332218 $, $Date: 2005-11-10 12:52:42 +0900 $
34   */
35  public abstract class AbstractMessageEncoder implements MessageEncoder
36  {
37      private final int type;
38  
39      protected AbstractMessageEncoder( int type )
40      {
41          this.type = type;
42      }
43  
44      public void encode( ProtocolSession session, Object message, ProtocolEncoderOutput out ) throws ProtocolViolationException
45      {
46          AbstractMessage m = ( AbstractMessage ) message ;
47          ByteBuffer buf = ByteBuffer.allocate( 16 );
48          buf.setAutoExpand( true ); // Enable auto-expand for easier encoding
49          
50          // Encode a header
51          buf.putShort( ( short ) type );
52          buf.putInt( m.getSequence() );
53          
54          // Encode a body
55          encodeBody( session, m, buf );
56          buf.flip();
57          out.write( buf );
58      }
59      
60      protected abstract void encodeBody( ProtocolSession session, AbstractMessage message, ByteBuffer out );
61  }