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 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 * @see DemuxingProtocolDecoder 37 * @see MessageDecoderFactory 38 */ 39 public interface MessageDecoder { 40 /** 41 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and 42 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please 43 * refer to each method's documentation for detailed explanation. 44 */ 45 static MessageDecoderResult OK = MessageDecoderResult.OK; 46 47 /** 48 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and 49 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please 50 * refer to each method's documentation for detailed explanation. 51 */ 52 static MessageDecoderResult NEED_DATA = MessageDecoderResult.NEED_DATA; 53 54 /** 55 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and 56 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please 57 * refer to each method's documentation for detailed explanation. 58 */ 59 static MessageDecoderResult NOT_OK = MessageDecoderResult.NOT_OK; 60 61 /** 62 * Checks the specified buffer is decodable by this decoder. 63 * 64 * @return {@link #OK} if this decoder can decode the specified buffer. 65 * {@link #NOT_OK} if this decoder cannot decode the specified buffer. 66 * {@link #NEED_DATA} if more data is required to determine if the 67 * specified buffer is decodable ({@link #OK}) or not decodable 68 * {@link #NOT_OK}. 69 */ 70 MessageDecoderResult decodable(IoSession session, IoBuffer in); 71 72 /** 73 * Decodes binary or protocol-specific content into higher-level message objects. 74 * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)} 75 * method with read data, and then the decoder implementation puts decoded 76 * messages into {@link ProtocolDecoderOutput}. 77 * 78 * @return {@link #OK} if you finished decoding messages successfully. 79 * {@link #NEED_DATA} if you need more data to finish decoding current message. 80 * {@link #NOT_OK} if you cannot decode current message due to protocol specification violation. 81 * 82 * @throws Exception if the read data violated protocol specification 83 */ 84 MessageDecoderResult decode(IoSession session, IoBuffer in, 85 ProtocolDecoderOutput out) throws Exception; 86 87 /** 88 * Invoked when the specified <tt>session</tt> is closed while this decoder was 89 * parsing the data. This method is useful when you deal with the protocol which doesn't 90 * specify the length of a message such as HTTP response without <tt>content-length</tt> 91 * header. Implement this method to process the remaining data that 92 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)} method didn't process 93 * completely. 94 * 95 * @throws Exception if the read data violated protocol specification 96 */ 97 void finishDecode(IoSession session, ProtocolDecoderOutput out) 98 throws Exception; 99 }