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1   /*
2    * Copyright 2015 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.protobuf;
17  
18  import com.google.protobuf.Message;
19  import com.google.protobuf.MessageLite;
20  import com.google.protobuf.MessageLiteOrBuilder;
21  import io.netty.buffer.ByteBuf;
22  import io.netty.channel.ChannelHandler.Sharable;
23  import io.netty.channel.ChannelHandlerContext;
24  import io.netty.channel.ChannelPipeline;
25  import io.netty.handler.codec.LengthFieldBasedFrameDecoder;
26  import io.netty.handler.codec.LengthFieldPrepender;
27  import io.netty.handler.codec.MessageToMessageEncoder;
28  
29  import java.util.List;
30  
31  import static io.netty.buffer.Unpooled.*;
32  
33  /**
34   * Encodes the requested <a href="https://github.com/google/protobuf">Google
35   * Protocol Buffers</a> {@link Message} and {@link MessageLite} into a
36   * {@link ByteBuf}. A typical setup for TCP/IP would be:
37   * <pre>
38   * {@link ChannelPipeline} pipeline = ...;
39   *
40   * // Decoders
41   * pipeline.addLast("frameDecoder",
42   *                  new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4));
43   * pipeline.addLast("protobufDecoder",
44   *                  new {@link ProtobufDecoder}(MyMessage.getDefaultInstance()));
45   *
46   * // Encoder
47   * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4));
48   * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}());
49   * </pre>
50   * and then you can use a {@code MyMessage} instead of a {@link ByteBuf}
51   * as a message:
52   * <pre>
53   * void channelRead({@link ChannelHandlerContext} ctx, Object msg) {
54   *     MyMessage req = (MyMessage) msg;
55   *     MyMessage res = MyMessage.newBuilder().setText(
56   *                               "Did you say '" + req.getText() + "'?").build();
57   *     ch.write(res);
58   * }
59   * </pre>
60   */
61  @Sharable
62  public class ProtobufEncoder extends MessageToMessageEncoder<MessageLiteOrBuilder> {
63      @Override
64      protected void encode(ChannelHandlerContext ctx, MessageLiteOrBuilder msg, List<Object> out)
65              throws Exception {
66          if (msg instanceof MessageLite) {
67              out.add(wrappedBuffer(((MessageLite) msg).toByteArray()));
68              return;
69          }
70          if (msg instanceof MessageLite.Builder) {
71              out.add(wrappedBuffer(((MessageLite.Builder) msg).build().toByteArray()));
72          }
73      }
74  }