View Javadoc
1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.handler.codec.marshalling;
17  
18  import java.io.StreamCorruptedException;
19  
20  import org.jboss.marshalling.ByteInput;
21  import org.jboss.marshalling.Unmarshaller;
22  import org.jboss.netty.buffer.ChannelBuffer;
23  import org.jboss.netty.channel.Channel;
24  import org.jboss.netty.channel.ChannelHandlerContext;
25  import org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
26  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
27  /**
28   * Decoder which MUST be used with {@link MarshallingEncoder}.
29   *
30   * A {@link LengthFieldBasedFrameDecoder} which use an {@link Unmarshaller} to read the Object out
31   * of the {@link ChannelBuffer}.
32   *
33   */
34  public class MarshallingDecoder extends LengthFieldBasedFrameDecoder {
35  
36      private final UnmarshallerProvider provider;
37  
38      /**
39       * Creates a new decoder whose maximum object size is {@code 1048576}
40       * bytes.  If the size of the received object is greater than
41       * {@code 1048576} bytes, a {@link StreamCorruptedException} will be
42       * raised.
43       *
44       */
45      public MarshallingDecoder(UnmarshallerProvider provider) {
46          this(provider, 1048576);
47      }
48  
49      /**
50       * Creates a new decoder with the specified maximum object size.
51       *
52       * @param maxObjectSize  the maximum byte length of the serialized object.
53       *                       if the length of the received object is greater
54       *                       than this value, {@link TooLongFrameException}
55       *                       will be raised.
56       */
57      public MarshallingDecoder(UnmarshallerProvider provider, int maxObjectSize) {
58          super(maxObjectSize, 0, 4, 0, 4);
59          this.provider = provider;
60      }
61  
62      @Override
63      protected Object decode(
64              ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer) throws Exception {
65  
66          ChannelBuffer frame = (ChannelBuffer) super.decode(ctx, channel, buffer);
67          if (frame == null) {
68              return null;
69          }
70  
71          Unmarshaller unmarshaller = provider.getUnmarshaller(ctx);
72          ByteInput input = new ChannelBufferByteInput(frame);
73  
74          try {
75              unmarshaller.start(input);
76              Object obj = unmarshaller.readObject();
77              unmarshaller.finish();
78              return obj;
79          } finally {
80              // Call close in a finally block as the ReplayingDecoder will throw an Error if not
81              // enough bytes are readable. This helps to be sure that we do not leak resource
82              unmarshaller.close();
83          }
84      }
85  
86      @Override
87      protected ChannelBuffer extractFrame(ChannelBuffer buffer, int index, int length) {
88          return buffer.slice(index, length);
89      }
90  }