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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 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 }