Java tutorial
/* * Copyright 2015 The Netty Project * * The Netty Project licenses this file to you under the Apache License, * version 2.0 (the "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at: * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the * License for the specific language governing permissions and limitations * under the License. */ package io.netty.handler.codec.protobuf; import com.google.protobuf.Message; import com.google.protobuf.MessageLite; import com.google.protobuf.MessageLiteOrBuilder; import io.netty.buffer.ByteBuf; import io.netty.channel.ChannelHandler.Sharable; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelPipeline; import io.netty.handler.codec.LengthFieldBasedFrameDecoder; import io.netty.handler.codec.LengthFieldPrepender; import io.netty.handler.codec.MessageToMessageEncoder; import java.util.List; import static io.netty.buffer.Unpooled.*; /** * Encodes the requested <a href="https://github.com/google/protobuf">Google * Protocol Buffers</a> {@link Message} and {@link MessageLite} into a * {@link ByteBuf}. A typical setup for TCP/IP would be: * <pre> * {@link ChannelPipeline} pipeline = ...; * * // Decoders * pipeline.addLast("frameDecoder", * new {@link LengthFieldBasedFrameDecoder}(1048576, 0, 4, 0, 4)); * pipeline.addLast("protobufDecoder", * new {@link ProtobufDecoder}(MyMessage.getDefaultInstance())); * * // Encoder * pipeline.addLast("frameEncoder", new {@link LengthFieldPrepender}(4)); * pipeline.addLast("protobufEncoder", new {@link ProtobufEncoder}()); * </pre> * and then you can use a {@code MyMessage} instead of a {@link ByteBuf} * as a message: * <pre> * void channelRead({@link ChannelHandlerContext} ctx, Object msg) { * MyMessage req = (MyMessage) msg; * MyMessage res = MyMessage.newBuilder().setText( * "Did you say '" + req.getText() + "'?").build(); * ch.write(res); * } * </pre> */ @Sharable public class ProtobufEncoder extends MessageToMessageEncoder<MessageLiteOrBuilder> { @Override protected void encode(ChannelHandlerContext ctx, MessageLiteOrBuilder msg, List<Object> out) throws Exception { if (msg instanceof MessageLite) { out.add(wrappedBuffer(((MessageLite) msg).toByteArray())); return; } if (msg instanceof MessageLite.Builder) { out.add(wrappedBuffer(((MessageLite.Builder) msg).build().toByteArray())); } } }