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 org.jboss.marshalling.ByteInput;
19  import org.jboss.marshalling.Unmarshaller;
20  import org.jboss.netty.buffer.ChannelBuffer;
21  import org.jboss.netty.channel.Channel;
22  import org.jboss.netty.channel.ChannelHandlerContext;
23  import org.jboss.netty.channel.ExceptionEvent;
24  import org.jboss.netty.handler.codec.frame.TooLongFrameException;
25  import org.jboss.netty.handler.codec.replay.ReplayingDecoder;
26  import org.jboss.netty.handler.codec.replay.VoidEnum;
27  
28  import java.io.ObjectStreamConstants;
29  
30  /**
31   * {@link ReplayingDecoder} which use an {@link Unmarshaller} to read the Object out of the {@link ChannelBuffer}.
32   *
33   * If you can you should use {@link MarshallingDecoder}.
34   *
35   *
36   *
37   */
38  public class CompatibleMarshallingDecoder extends ReplayingDecoder<VoidEnum> {
39      protected final UnmarshallerProvider provider;
40      protected final int maxObjectSize;
41      private boolean discardingTooLongFrame;
42  
43      /**
44       * Create a new instance of {@link CompatibleMarshallingDecoder}.
45       *
46       * @param provider
47       *        the {@link UnmarshallerProvider} which is used to obtain the {@link Unmarshaller}
48       *        for the {@link Channel}
49       * @param maxObjectSize
50       *        the maximal size (in bytes) of the {@link Object} to unmarshal. Once the size is
51       *        exceeded the {@link Channel} will get closed. Use a a maxObjectSize of
52       *        {@link Integer#MAX_VALUE} to disable this. You should only do this if you are sure
53       *        that the received Objects will never be big and the sending side are trusted, as
54       *        this opens the possibility for a DOS-Attack due an {@link OutOfMemoryError}.
55       */
56      public CompatibleMarshallingDecoder(UnmarshallerProvider provider, int maxObjectSize) {
57          this.provider = provider;
58          this.maxObjectSize = maxObjectSize;
59      }
60  
61      @Override
62      protected Object decode(
63              ChannelHandlerContext ctx, Channel channel, ChannelBuffer buffer, VoidEnum state) throws Exception {
64          if (discardingTooLongFrame) {
65              buffer.skipBytes(actualReadableBytes());
66              checkpoint();
67              return null;
68          }
69  
70          Unmarshaller unmarshaller = provider.getUnmarshaller(ctx);
71          ByteInput input = new ChannelBufferByteInput(buffer);
72          if (maxObjectSize != Integer.MAX_VALUE) {
73              input = new LimitingByteInput(input, maxObjectSize);
74          }
75          try {
76              unmarshaller.start(input);
77              Object obj = unmarshaller.readObject();
78              unmarshaller.finish();
79              return obj;
80          } catch (LimitingByteInput.TooBigObjectException e) {
81              discardingTooLongFrame = true;
82              throw new TooLongFrameException();
83          } finally {
84              // Call close in a finally block as the ReplayingDecoder will throw an Error if not enough bytes are
85              // readable. This helps to be sure that we do not leak resource
86              unmarshaller.close();
87          }
88      }
89  
90      @Override
91      protected Object decodeLast(ChannelHandlerContext ctx, Channel channel,
92              ChannelBuffer buffer, VoidEnum state)
93              throws Exception {
94          switch (buffer.readableBytes()) {
95          case 0:
96              return null;
97          case 1:
98              // Ignore the last TC_RESET
99              if (buffer.getByte(buffer.readerIndex()) == ObjectStreamConstants.TC_RESET) {
100                 buffer.skipBytes(1);
101                 return null;
102             }
103         }
104 
105         Object decoded = decode(ctx, channel, buffer, state);
106         return decoded;
107     }
108 
109     /**
110      * Calls {@link Channel#close()} if a TooLongFrameException was thrown
111      */
112     @Override
113     public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
114         if (e.getCause() instanceof TooLongFrameException) {
115             e.getChannel().close();
116         } else {
117             super.exceptionCaught(ctx, e);
118         }
119     }
120 }