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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.protobuf;
17  
18  import org.jboss.netty.buffer.ChannelBuffer;
19  import org.jboss.netty.channel.Channel;
20  import org.jboss.netty.channel.ChannelHandler.Sharable;
21  import org.jboss.netty.channel.ChannelHandlerContext;
22  import org.jboss.netty.channel.ChannelPipeline;
23  import org.jboss.netty.channel.MessageEvent;
24  import org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
25  import org.jboss.netty.handler.codec.frame.LengthFieldPrepender;
26  import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
27  
28  import com.google.protobuf.Message;
29  import com.google.protobuf.MessageLite;
30  
31  /**
32   * Encodes the requested <a href="http://code.google.com/p/protobuf/">Google
33   * Protocol Buffers</a> {@link Message} and {@link MessageLite} into a
34   * {@link ChannelBuffer}. A typical setup for TCP/IP would be:
35   * <pre>
36   * {@link ChannelPipeline} pipeline = ...;
37   *
38   * // Decoders
39   * pipeline.addLast("frameDecoder",
40   *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
41   * pipeline.addLast("protobufDecoder",
42   *                  new {@link ProtobufDecoder}(MyMessage.getDefaultInstance()));
43   *
44   * // Encoder
45   * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
46   * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}());
47   * </pre>
48   * and then you can use a {@code MyMessage} instead of a {@link ChannelBuffer}
49   * as a message:
50   * <pre>
51   * void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
52   *     MyMessage req = (MyMessage) e.getMessage();
53   *     MyMessage res = MyMessage.newBuilder().setText(
54   *                               "Did you say '" + req.getText() + "'?").build();
55   *     ch.write(res);
56   * }
57   * </pre>
58   *
59   * @apiviz.landmark
60   */
61  @Sharable
62  public class ProtobufEncoder extends OneToOneEncoder {
63  
64      @Override
65      protected Object encode(
66              ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
67          if (msg instanceof MessageLite) {
68              byte[] array = ((MessageLite) msg).toByteArray();
69              return ctx.getChannel().getConfig().getBufferFactory().getBuffer(array, 0, array.length);
70          }
71          if (msg instanceof MessageLite.Builder) {
72              byte[] array = ((MessageLite.Builder) msg).build().toByteArray();
73              return ctx.getChannel().getConfig().getBufferFactory().getBuffer(array, 0, array.length);
74          }
75          return msg;
76      }
77  }