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.serialization;
17  
18  import java.io.ObjectInputStream;
19  import java.io.ObjectOutputStream;
20  import java.io.OutputStream;
21  import java.util.concurrent.atomic.AtomicReference;
22  
23  import org.jboss.netty.buffer.ChannelBuffer;
24  import org.jboss.netty.buffer.ChannelBufferFactory;
25  import org.jboss.netty.buffer.ChannelBufferOutputStream;
26  import org.jboss.netty.buffer.ChannelBuffers;
27  import org.jboss.netty.channel.Channel;
28  import org.jboss.netty.channel.ChannelHandlerContext;
29  import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
30  
31  /**
32   * An encoder which serializes a Java object into a {@link ChannelBuffer}
33   * (interoperability version).
34   * <p>
35   * This encoder is interoperable with the standard Java object streams such as
36   * {@link ObjectInputStream} and {@link ObjectOutputStream}.
37   */
38  public class CompatibleObjectEncoder extends OneToOneEncoder {
39  
40      private final AtomicReference<ChannelBuffer> buffer =
41          new AtomicReference<ChannelBuffer>();
42      private final int resetInterval;
43      private volatile ObjectOutputStream oout;
44      private int writtenObjects;
45  
46      /**
47       * Creates a new instance with the reset interval of {@code 16}.
48       */
49      public CompatibleObjectEncoder() {
50          this(16); // Reset at every sixteen writes
51      }
52  
53      /**
54       * Creates a new instance.
55       *
56       * @param resetInterval
57       *        the number of objects between {@link ObjectOutputStream#reset()}.
58       *        {@code 0} will disable resetting the stream, but the remote
59       *        peer will be at the risk of getting {@link OutOfMemoryError} in
60       *        the long term.
61       */
62      public CompatibleObjectEncoder(int resetInterval) {
63          if (resetInterval < 0) {
64              throw new IllegalArgumentException(
65                      "resetInterval: " + resetInterval);
66          }
67          this.resetInterval = resetInterval;
68      }
69  
70      /**
71       * Creates a new {@link ObjectOutputStream} which wraps the specified
72       * {@link OutputStream}.  Override this method to use a subclass of the
73       * {@link ObjectOutputStream}.
74       */
75      protected ObjectOutputStream newObjectOutputStream(OutputStream out) throws Exception {
76          return new ObjectOutputStream(out);
77      }
78  
79      @Override
80      protected Object encode(ChannelHandlerContext context, Channel channel, Object msg) throws Exception {
81          ChannelBuffer buffer = buffer(context);
82          ObjectOutputStream oout = this.oout;
83          if (resetInterval != 0) {
84              // Resetting will prevent OOM on the receiving side.
85              writtenObjects ++;
86              if (writtenObjects % resetInterval == 0) {
87                  oout.reset();
88  
89                  // Also discard the byproduct to avoid OOM on the sending side.
90                  buffer.discardReadBytes();
91              }
92          }
93          oout.writeObject(msg);
94          oout.flush();
95  
96          ChannelBuffer encoded = buffer.readBytes(buffer.readableBytes());
97          return encoded;
98      }
99  
100     private ChannelBuffer buffer(ChannelHandlerContext ctx) throws Exception {
101         ChannelBuffer buf = buffer.get();
102         if (buf == null) {
103             ChannelBufferFactory factory = ctx.getChannel().getConfig().getBufferFactory();
104             buf = ChannelBuffers.dynamicBuffer(factory);
105             if (buffer.compareAndSet(null, buf)) {
106                 boolean success = false;
107                 try {
108                     oout = newObjectOutputStream(new ChannelBufferOutputStream(buf));
109                     success = true;
110                 } finally {
111                     if (!success) {
112                         oout = null;
113                     }
114                 }
115             } else {
116                 buf = buffer.get();
117             }
118         }
119         return buf;
120     }
121 }