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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 io.netty.handler.codec.marshalling;
17  
18  import io.netty.buffer.ByteBuf;
19  import io.netty.channel.ChannelHandlerContext;
20  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
21  import io.netty.handler.codec.TooLongFrameException;
22  import org.jboss.marshalling.ByteInput;
23  import org.jboss.marshalling.Unmarshaller;
24  
25  import java.io.StreamCorruptedException;
26  /**
27   * Decoder which MUST be used with {@link MarshallingEncoder}.
28   *
29   * A {@link LengthFieldBasedFrameDecoder} which use an {@link Unmarshaller} to read the Object out
30   * of the {@link ByteBuf}.
31   *
32   */
33  public class MarshallingDecoder extends LengthFieldBasedFrameDecoder {
34  
35      private final UnmarshallerProvider provider;
36  
37      /**
38       * Creates a new decoder whose maximum object size is {@code 1048576}
39       * bytes.  If the size of the received object is greater than
40       * {@code 1048576} bytes, a {@link StreamCorruptedException} will be
41       * raised.
42       *
43       */
44      public MarshallingDecoder(UnmarshallerProvider provider) {
45          this(provider, 1048576);
46      }
47  
48      /**
49       * Creates a new decoder with the specified maximum object size.
50       *
51       * @param maxObjectSize  the maximum byte length of the serialized object.
52       *                       if the length of the received object is greater
53       *                       than this value, {@link TooLongFrameException}
54       *                       will be raised.
55       */
56      public MarshallingDecoder(UnmarshallerProvider provider, int maxObjectSize) {
57          super(maxObjectSize, 0, 4, 0, 4);
58          this.provider = provider;
59      }
60  
61      @Override
62      protected Object decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception {
63          ByteBuf frame = (ByteBuf) super.decode(ctx, in);
64          if (frame == null) {
65              return null;
66          }
67  
68          Unmarshaller unmarshaller = provider.getUnmarshaller(ctx);
69          ByteInput input = new ChannelBufferByteInput(frame);
70  
71          try {
72              unmarshaller.start(input);
73              Object obj = unmarshaller.readObject();
74              unmarshaller.finish();
75              return obj;
76          } finally {
77              // Call close in a finally block as the ReplayingDecoder will throw an Error if not enough bytes are
78              // readable. This helps to be sure that we do not leak resource
79              unmarshaller.close();
80          }
81      }
82  
83      @Override
84      protected ByteBuf extractFrame(ChannelHandlerContext ctx, ByteBuf buffer, int index, int length) {
85          return buffer.slice(index, length);
86      }
87  }