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Java > Open Source Codes > org > apache > mina > example > sumup > codec > AbstractMessageDecoder


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.ProtocolDecoderOutput;
26 import org.apache.mina.filter.codec.demux.MessageDecoder;
27 import org.apache.mina.filter.codec.demux.MessageDecoderResult;
28
29 /**
30  * A {@link MessageDecoder} that decodes message header and forwards
31  * the decoding of body to a subclass.
32  *
33  * @author The Apache Directory Project (mina-dev@directory.apache.org)
34  * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (금, 13 7월 2007) $
35  */
36 public abstract class AbstractMessageDecoder implements MessageDecoder {
37     private final int type;
38
39     private int sequence;
40
41     private boolean readHeader;
42
43     protected AbstractMessageDecoder(int type) {
44         this.type = type;
45     }
46
47     public MessageDecoderResult decodable(IoSession session, ByteBuffer in) {
48         // Return NEED_DATA if the whole header is not read yet.
49 if (in.remaining() < Constants.HEADER_LEN) {
50             return MessageDecoderResult.NEED_DATA;
51         }
52
53         // Return OK if type and bodyLength matches.
54 if (type == in.getShort()) {
55             return MessageDecoderResult.OK;
56         }
57
58         // Return NOT_OK if not matches.
59 return MessageDecoderResult.NOT_OK;
60     }
61
62     public MessageDecoderResult decode(IoSession session, ByteBuffer in,
63             ProtocolDecoderOutput out) throws Exception JavaDoc {
64         // Try to skip header if not read.
65 if (!readHeader) {
66             in.getShort(); // Skip 'type'.
67 sequence = in.getInt(); // Get 'sequence'.
68 readHeader = true;
69         }
70
71         // Try to decode body
72 AbstractMessage m = decodeBody(session, in);
73         // Return NEED_DATA if the body is not fully read.
74 if (m == null) {
75             return MessageDecoderResult.NEED_DATA;
76         } else {
77             readHeader = false; // reset readHeader for the next decode
78 }
79         m.setSequence(sequence);
80         out.write(m);
81
82         return MessageDecoderResult.OK;
83     }
84
85     /**
86      * @return <tt>null</tt> if the whole body is not read yet
87      */
88     protected abstract AbstractMessage decodeBody(IoSession session,
89             ByteBuffer in);
90 }
91
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