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 static org.jboss.netty.buffer.ChannelBuffers.*;
19
20 import org.jboss.netty.buffer.ChannelBuffer;
21 import org.jboss.netty.channel.Channel;
22 import org.jboss.netty.channel.ChannelHandler.Sharable;
23 import org.jboss.netty.channel.ChannelHandlerContext;
24 import org.jboss.netty.channel.ChannelPipeline;
25 import org.jboss.netty.channel.MessageEvent;
26 import org.jboss.netty.handler.codec.frame.LengthFieldBasedFrameDecoder;
27 import org.jboss.netty.handler.codec.frame.LengthFieldPrepender;
28 import org.jboss.netty.handler.codec.oneone.OneToOneEncoder;
29
30 import com.google.protobuf.Message;
31 import com.google.protobuf.MessageLite;
32
33 /**
34 * Encodes the requested <a href="http://code.google.com/p/protobuf/">Google
35 * Protocol Buffers</a> {@link Message} and {@link MessageLite} into a
36 * {@link ChannelBuffer}. 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 ChannelBuffer}
51 * as a message:
52 * <pre>
53 * void messageReceived({@link ChannelHandlerContext} ctx, {@link MessageEvent} e) {
54 * MyMessage req = (MyMessage) e.getMessage();
55 * MyMessage res = MyMessage.newBuilder().setText(
56 * "Did you say '" + req.getText() + "'?").build();
57 * ch.write(res);
58 * }
59 * </pre>
60 *
61 * @apiviz.landmark
62 */
63 @Sharable
64 public class ProtobufEncoder extends OneToOneEncoder {
65
66 @Override
67 protected Object encode(
68 ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
69 if (msg instanceof MessageLite) {
70 return wrappedBuffer(((MessageLite) msg).toByteArray());
71 }
72 if (msg instanceof MessageLite.Builder) {
73 return wrappedBuffer(((MessageLite.Builder) msg).build().toByteArray());
74 }
75 return msg;
76 }
77 }