【Netty系列】Protobuf编码解码：客户端、服务端

以下是一个完整的Netty + Protobuf实际案例，包含服务端和客户端实现：

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步骤1：定义Protobuf协议

创建message.proto文件：

syntax = "proto3";option java_package = "com.example.netty.protobuf";
option java_outer_classname = "MessageProto";message Message {int32 id = 1;string content = 2;MessageType type = 3;enum MessageType {REQUEST = 0;RESPONSE = 1;}
}

生成Java类：

protoc --java_out=./src/main/java message.proto

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步骤2：服务端实现

// Server.java
public class Server {public static void main(String[] args) throws Exception {EventLoopGroup bossGroup = new NioEventLoopGroup();EventLoopGroup workerGroup = new NioEventLoopGroup();try {ServerBootstrap b = new ServerBootstrap();b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class).childHandler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) {ChannelPipeline pipeline = ch.pipeline();// 解码器pipeline.addLast(new ProtobufVarint32FrameDecoder());pipeline.addLast(new ProtobufDecoder(MessageProto.Message.getDefaultInstance()));// 编码器pipeline.addLast(new ProtobufVarint32LengthFieldPrepender());pipeline.addLast(new ProtobufEncoder());// 业务处理器pipeline.addLast(new ServerHandler());}});ChannelFuture f = b.bind(8888).sync();f.channel().closeFuture().sync();} finally {workerGroup.shutdownGracefully();bossGroup.shutdownGracefully();}}
}// ServerHandler.java
public class ServerHandler extends SimpleChannelInboundHandler<MessageProto.Message> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, MessageProto.Message msg) {System.out.println("Server received: " + msg.getContent());// 构建响应MessageProto.Message response = MessageProto.Message.newBuilder().setId(msg.getId()).setContent("Response to: " + msg.getContent()).setType(MessageProto.Message.MessageType.RESPONSE).build();ctx.writeAndFlush(response);}
}

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步骤3：客户端实现

// Client.java
public class Client {public static void main(String[] args) throws Exception {EventLoopGroup group = new NioEventLoopGroup();try {Bootstrap b = new Bootstrap();b.group(group).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {@Overrideprotected void initChannel(SocketChannel ch) {ChannelPipeline pipeline = ch.pipeline();pipeline.addLast(new ProtobufVarint32FrameDecoder());pipeline.addLast(new ProtobufDecoder(MessageProto.Message.getDefaultInstance()));pipeline.addLast(new ProtobufVarint32LengthFieldPrepender());pipeline.addLast(new ProtobufEncoder());pipeline.addLast(new ClientHandler());}});ChannelFuture f = b.connect("localhost", 8888).sync();// 发送消息MessageProto.Message request = MessageProto.Message.newBuilder().setId(1).setContent("Hello Server").setType(MessageProto.Message.MessageType.REQUEST).build();f.channel().writeAndFlush(request);f.channel().closeFuture().sync();} finally {group.shutdownGracefully();}}
}// ClientHandler.java
public class ClientHandler extends SimpleChannelInboundHandler<MessageProto.Message> {@Overrideprotected void channelRead0(ChannelHandlerContext ctx, MessageProto.Message msg) {System.out.println("Client received: " + msg.getContent());}
}

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关键点说明

1. 编解码器链配置：

• • ProtobufVarint32FrameDecoder：处理TCP粘包/拆包
  • ProtobufDecoder：将字节流转换为Protobuf对象
  • ProtobufVarint32LengthFieldPrepender：添加长度前缀
  • ProtobufEncoder：将Protobuf对象序列化为字节流

1. 消息流转：

客户端发送: Protobuf对象 → 编码 → 字节流 → 网络传输
服务端接收: 字节流 → 解码 → Protobuf对象 → 业务处理

1. 性能优化：

• • 复用Protobuf对象实例（getDefaultInstance()）
  • 使用Unpooled直接内存分配（示例中Netty已自动优化）

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运行测试

1. 先启动服务端
2. 再启动客户端
3. 观察控制台输出：

Server received: Hello Server
Client received: Response to: Hello Server

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扩展建议

1. 添加SSL加密：

pipeline.addFirst(new SslHandler(sslEngine));

1. 使用LengthFieldBasedFrameDecoder替代Protobuf自带拆包器
2. 结合ByteToMessageCodec实现复合消息处理

这个示例完整展示了Netty与Protobuf的整合，实现了二进制数据的高效传输。实际生产环境中可根据需要添加心跳机制、重连策略等扩展功能。