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.filter.codec.demux;
21
22 import org.apache.mina.core.buffer.IoBuffer;
23 import org.apache.mina.core.session.IoSession;
24 import org.apache.mina.filter.codec.ProtocolDecoderOutput;
25
26 /**
27 * Decodes a certain type of messages.
28 * <p>
29 * We didn't provide any <tt>dispose</tt> method for {@link MessageDecoder}
30 * because it can give you performance penalty in case you have a lot of
31 * message types to handle.
32 *
33 * @author <a href="http://mina.apache.org">Apache MINA Project</a>
34 *
35 * @see DemuxingProtocolDecoder
36 * @see MessageDecoderFactory
37 */
38 public interface MessageDecoder {
39 /**
40 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and
41 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please
42 * refer to each method's documentation for detailed explanation.
43 */
44 MessageDecoderResult OK = MessageDecoderResult.OK;
45
46 /**
47 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and
48 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please
49 * refer to each method's documentation for detailed explanation.
50 */
51 MessageDecoderResult NEED_DATA = MessageDecoderResult.NEED_DATA;
52
53 /**
54 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and
55 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please
56 * refer to each method's documentation for detailed explanation.
57 */
58 MessageDecoderResult NOT_OK = MessageDecoderResult.NOT_OK;
59
60 /**
61 * Checks the specified buffer is decodable by this decoder.
62 *
63 * @param session The current session
64 * @param in The buffer containing the data to decode
65 * @return {@link #OK} if this decoder can decode the specified buffer.
66 * {@link #NOT_OK} if this decoder cannot decode the specified buffer.
67 * {@link #NEED_DATA} if more data is required to determine if the
68 * specified buffer is decodable ({@link #OK}) or not decodable
69 * {@link #NOT_OK}.
70 */
71 MessageDecoderResult decodable(IoSession session, IoBuffer in);
72
73 /**
74 * Decodes binary or protocol-specific content into higher-level message objects.
75 * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}
76 * method with read data, and then the decoder implementation puts decoded
77 * messages into {@link ProtocolDecoderOutput}.
78 *
79 * @param session The current session
80 * @param in The buffer containing the data to decode
81 * @param out The instance of {@link ProtocolDecoderOutput} that will receive the decoded messages
82 * @return {@link #OK} if you finished decoding messages successfully.
83 * {@link #NEED_DATA} if you need more data to finish decoding current message.
84 * {@link #NOT_OK} if you cannot decode current message due to protocol specification violation.
85 * @throws Exception if the read data violated protocol specification
86 */
87 MessageDecoderResult decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception;
88
89 /**
90 * Invoked when the specified <tt>session</tt> is closed while this decoder was
91 * parsing the data. This method is useful when you deal with the protocol which doesn't
92 * specify the length of a message such as HTTP response without <tt>content-length</tt>
93 * header. Implement this method to process the remaining data that
94 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)} method didn't process
95 * completely.
96 *
97 * @param session The current session
98 * @param out The instance of {@link ProtocolDecoderOutput} that contains the decoded messages
99 * @throws Exception if the read data violated protocol specification
100 */
101 void finishDecode(IoSession session, ProtocolDecoderOutput out) throws Exception;
102 }