001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 * 019 */ 020package org.apache.mina.filter.codec.demux; 021 022import org.apache.mina.core.buffer.IoBuffer; 023import org.apache.mina.core.session.IoSession; 024import org.apache.mina.filter.codec.ProtocolDecoderOutput; 025 026/** 027 * Decodes a certain type of messages. 028 * <p> 029 * We didn't provide any <tt>dispose</tt> method for {@link MessageDecoder} 030 * because it can give you performance penalty in case you have a lot of 031 * message types to handle. 032 * 033 * @author <a href="http://mina.apache.org">Apache MINA Project</a> 034 * 035 * @see DemuxingProtocolDecoder 036 * @see MessageDecoderFactory 037 */ 038public interface MessageDecoder { 039 /** 040 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and 041 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please 042 * refer to each method's documentation for detailed explanation. 043 */ 044 MessageDecoderResult OK = MessageDecoderResult.OK; 045 046 /** 047 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and 048 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please 049 * refer to each method's documentation for detailed explanation. 050 */ 051 MessageDecoderResult NEED_DATA = MessageDecoderResult.NEED_DATA; 052 053 /** 054 * Represents a result from {@link #decodable(IoSession, IoBuffer)} and 055 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)}. Please 056 * refer to each method's documentation for detailed explanation. 057 */ 058 MessageDecoderResult NOT_OK = MessageDecoderResult.NOT_OK; 059 060 /** 061 * Checks the specified buffer is decodable by this decoder. 062 * 063 * @param session The current session 064 * @param in The buffer containing the data to decode 065 * @return {@link #OK} if this decoder can decode the specified buffer. 066 * {@link #NOT_OK} if this decoder cannot decode the specified buffer. 067 * {@link #NEED_DATA} if more data is required to determine if the 068 * specified buffer is decodable ({@link #OK}) or not decodable 069 * {@link #NOT_OK}. 070 */ 071 MessageDecoderResult decodable(IoSession session, IoBuffer in); 072 073 /** 074 * Decodes binary or protocol-specific content into higher-level message objects. 075 * MINA invokes {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)} 076 * method with read data, and then the decoder implementation puts decoded 077 * messages into {@link ProtocolDecoderOutput}. 078 * 079 * @param session The current session 080 * @param in The buffer containing the data to decode 081 * @param out The instance of {@link ProtocolDecoderOutput} that will receive the decoded messages 082 * @return {@link #OK} if you finished decoding messages successfully. 083 * {@link #NEED_DATA} if you need more data to finish decoding current message. 084 * {@link #NOT_OK} if you cannot decode current message due to protocol specification violation. 085 * @throws Exception if the read data violated protocol specification 086 */ 087 MessageDecoderResult decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws Exception; 088 089 /** 090 * Invoked when the specified <tt>session</tt> is closed while this decoder was 091 * parsing the data. This method is useful when you deal with the protocol which doesn't 092 * specify the length of a message such as HTTP response without <tt>content-length</tt> 093 * header. Implement this method to process the remaining data that 094 * {@link #decode(IoSession, IoBuffer, ProtocolDecoderOutput)} method didn't process 095 * completely. 096 * 097 * @param session The current session 098 * @param out The instance of {@link ProtocolDecoderOutput} that contains the decoded messages 099 * @throws Exception if the read data violated protocol specification 100 */ 101 void finishDecode(IoSession session, ProtocolDecoderOutput out) throws Exception; 102}