Java tutorial
package com.chat.common.netty.handler.decode; /* * 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. */ import com.google.protobuf.ExtensionRegistry; import com.google.protobuf.ExtensionRegistryLite; import com.google.protobuf.Message; import com.google.protobuf.MessageLite; 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.ByteToMessageDecoder; import io.netty.handler.codec.LengthFieldBasedFrameDecoder; import io.netty.handler.codec.LengthFieldPrepender; import io.netty.handler.codec.MessageToMessageDecoder; import java.util.List; /** * Decodes a received {@link ByteBuf} into a * <a href="http://code.google.com/p/protobuf/">Google Protocol Buffers</a> * {@link Message} and {@link MessageLite}. Please note that this decoder must * be used with a proper {@link ByteToMessageDecoder} such as {@link ProtobufVarint32FrameDecoder} * or {@link LengthFieldBasedFrameDecoder} if you are using a stream-based * transport such as TCP/IP. 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 ProtobufDecoder extends MessageToMessageDecoder<ByteBuf> { private static final boolean HAS_PARSER; static { boolean hasParser = false; try { // MessageLite.getParsetForType() is not available until protobuf 2.5.0. MessageLite.class.getDeclaredMethod("getParserForType"); hasParser = true; } catch (Throwable t) { // Ignore } HAS_PARSER = hasParser; } private final MessageLite prototype; private final ExtensionRegistryLite extensionRegistry; /** * Creates a new instance. */ public ProtobufDecoder(MessageLite prototype) { this(prototype, null); } public ProtobufDecoder(MessageLite prototype, ExtensionRegistry extensionRegistry) { this(prototype, (ExtensionRegistryLite) extensionRegistry); } public ProtobufDecoder(MessageLite prototype, ExtensionRegistryLite extensionRegistry) { if (prototype == null) { throw new NullPointerException("prototype"); } this.prototype = prototype.getDefaultInstanceForType(); this.extensionRegistry = extensionRegistry; } @Override protected void decode(ChannelHandlerContext ctx, ByteBuf msg, List<Object> out) throws Exception { final byte[] array; final int offset; final int length = msg.readableBytes(); if (msg.hasArray()) { array = msg.array(); offset = msg.arrayOffset() + msg.readerIndex(); } else { array = new byte[length]; msg.getBytes(msg.readerIndex(), array, 0, length); offset = 0; } if (extensionRegistry == null) { if (HAS_PARSER) { out.add(prototype.getParserForType().parseFrom(array, offset, length)); } else { out.add(prototype.newBuilderForType().mergeFrom(array, offset, length).build()); } } else { if (HAS_PARSER) { out.add(prototype.getParserForType().parseFrom(array, offset, length, extensionRegistry)); } else { out.add(prototype.newBuilderForType().mergeFrom(array, offset, length, extensionRegistry).build()); } } } }