View Javadoc

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.codec;
21  
22  import java.nio.ByteBuffer;
23  
24  /**
25   * Decodes binary or protocol-specific data into higher-level message objects.
26   * 
27   * Must be immutable, a CONTEXT will be provided per session.
28   * 
29   * @param <INPUT> the incoming message to decode (the low level message, usually a {@link ByteBuffer})
30   * @param <OUTPUT> the decoded message (your high level protocol Pojo/DTO)
31   * @param <DECODING_STATE> the context where to save the current decoding state (e.g. accumulated bytes, encoding
32   *        context switching..)
33   * 
34   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
35   * 
36   */
37  public interface ProtocolDecoder<INPUT, OUTPUT, DECODING_STATE> {
38  
39      /**
40       * Create a new session context for this decoder
41       * 
42       * @return the newly created context
43       */
44      DECODING_STATE createDecoderState();
45  
46      /**
47       * Decode binary or protocol-specific content of type <code>INPUT</code> into higher-level protocol message objects,
48       * of type OUTPUT
49       * 
50       * @param input the received message to decode
51       * @param context the decoding context (will be stored in the session for the next decode call)
52       * @return the decoded message or <code>null</code> if nothing was decoded
53       */
54      OUTPUT decode(INPUT input, DECODING_STATE context);
55  
56      /**
57       * Finish decoding, for example if the decoder accumulated some unused input, it should discard it, or throw an
58       * Exception
59       */
60      void finishDecode(DECODING_STATE context);
61  }