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.core.buffer.IoBuffer;
23 import org.apache.mina.core.session.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 MINA Project (dev@mina.apache.org)
34 * @version $Rev: 671827 $, $Date: 2008-06-26 10:49:48 +0200 (jeu, 26 jun 2008) $
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, IoBuffer 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, IoBuffer in,
63 ProtocolDecoderOutput out) throws Exception {
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 IoBuffer in);
90 }