netty 的 Google protobuf 开发

时间：2023-03-08 19:15:13
netty 的 Google protobuf 开发

根据上一篇博文 Google Protobuf 使用 Java 版 netty 集成 protobuf 的方法非常简单.代码如下:

server

package protobuf.server.impl;

import io.netty.bootstrap.ServerBootstrap;

import io.netty.channel.ChannelFuture;

import io.netty.channel.ChannelInitializer;

import io.netty.channel.ChannelOption;

import io.netty.channel.nio.NioEventLoopGroup;

import io.netty.channel.socket.SocketChannel;

import io.netty.channel.socket.nio.NioServerSocketChannel;

import io.netty.handler.codec.protobuf.ProtobufDecoder;

import io.netty.handler.codec.protobuf.ProtobufEncoder;

import io.netty.handler.codec.protobuf.ProtobufVarint32FrameDecoder;

import io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender;

import io.netty.handler.logging.LogLevel;

import io.netty.handler.logging.LoggingHandler;

import object.server.impl.SubReqServer;

import object.server.impl.SubScriptReqProto;

public class SubReqProtobufServer {

    public void start(int port) {

        NioEventLoopGroup workGroup = new NioEventLoopGroup();

        NioEventLoopGroup bossGroup = new NioEventLoopGroup();

        ServerBootstrap bootstrap = new ServerBootstrap();

        bootstrap.group(bossGroup, workGroup);

        bootstrap.channel(NioServerSocketChannel.class);

        // 配置 NioServerSocketChannel 的 tcp 参数, BACKLOG 的大小

        bootstrap.option(ChannelOption.SO_BACKLOG, 100);

        bootstrap.handler(new LoggingHandler(LogLevel.INFO));

        bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {

            protected void initChannel(SocketChannel ch) throws Exception {

                /*

                 * 首先添加 ProtobufVarint32FrameDecoder 处理器 , 它主要用于半包处理

                 */

                ch.pipeline().addLast(new ProtobufVarint32FrameDecoder());

                /*

                 * 然后添加 ProtobufDecoder 解码器 ,

                 * 他的参数com.google.protobuf.MessageLite 实际上就是要告诉 ProtobufDecoder

                 * 需要解码的目标类是什么,否则仅仅从字节数组中是无法判断出需要解码的目标类型信息

                 */

                ProtobufDecoder protobufDecoder = new ProtobufDecoder(

                        SubScriptReqProto.SubScriptReq.getDefaultInstance());

                ch.pipeline().addLast(protobufDecoder);

                ch.pipeline().addLast(

                        new ProtobufVarint32LengthFieldPrepender());

                ch.pipeline().addLast(new ProtobufEncoder());

                ch.pipeline().addLast(new SubReqProtobufHandler());

            }

        });

        // 绑定端口,随后调用它的同步阻塞方法 sync 等等绑定操作成功,完成之后 Netty 会返回一个 ChannelFuture

        // 它的功能类似于的 Future,主要用于异步操作的通知回调.

        ChannelFuture channelFuture;

        try {

            channelFuture = bootstrap.bind(port).sync();

            // 等待服务端监听端口关闭,调用 sync 方法进行阻塞,等待服务端链路关闭之后 main 函数才退出.

            channelFuture.channel().closeFuture().sync();

        } catch (InterruptedException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        } finally {

            bossGroup.shutdownGracefully();

            workGroup.shutdownGracefully();

        }

    }

    public static void main(String[] args) {

        SubReqProtobufServer server = new SubReqProtobufServer();

        server.start(9091);

    }

}

serverHandler

package protobuf.server.impl;

import object.server.impl.SubScriptReqProto;

import object.server.impl.SubScriptRespProto;

import io.netty.channel.ChannelHandlerAdapter;

import io.netty.channel.ChannelHandlerContext;

public class SubReqProtobufHandler extends ChannelHandlerAdapter {

    @Override

    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)

            throws Exception {

        cause.printStackTrace();

        ctx.close();

    }

    @Override

    public void channelRead(ChannelHandlerContext ctx, Object msg)

            throws Exception {

        try {

            SubScriptReqProto.SubScriptReq req = (SubScriptReqProto.SubScriptReq) msg;

            System.out.println("SubReqProtobufHandler : " + req);

            ctx.writeAndFlush(resp(req.getSubReqID()));

        } catch (Exception e) {

            e.printStackTrace();

            throw e;

        }

    }

    private Object resp(int subReqID) {

        SubScriptRespProto.SubScriptResp.Builder builder = SubScriptRespProto.SubScriptResp

                .newBuilder();

        builder.setSubReqID(subReqID);

        builder.setDesc("desc");

        builder.setRespCode(2);

        return builder.build();

    }

    @Override

    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

        ctx.flush();

    }

}

client

package protobuf.client.impl;

import io.netty.bootstrap.Bootstrap;

import io.netty.channel.ChannelFuture;

import io.netty.channel.ChannelInitializer;

import io.netty.channel.ChannelOption;

import io.netty.channel.nio.NioEventLoopGroup;

import io.netty.channel.socket.SocketChannel;

import io.netty.channel.socket.nio.NioSocketChannel;

import io.netty.handler.codec.protobuf.ProtobufDecoder;

import io.netty.handler.codec.protobuf.ProtobufEncoder;

import io.netty.handler.codec.protobuf.ProtobufVarint32FrameDecoder;

import io.netty.handler.codec.protobuf.ProtobufVarint32LengthFieldPrepender;

import io.netty.handler.codec.serialization.ObjectEncoder;

import object.client.impl.SubReqClient;

import object.server.impl.SubScriptReqProto;

import object.server.impl.SubScriptRespProto;

public class SubReqProtobufClient {

    public void connect(String host, int port) {

        NioEventLoopGroup workGroup = new NioEventLoopGroup();

        Bootstrap bootstrap = new Bootstrap();

        bootstrap.group(workGroup);

        bootstrap.channel(NioSocketChannel.class);

        bootstrap.option(ChannelOption.TCP_NODELAY, true);

        bootstrap.handler(new ChannelInitializer<SocketChannel>() {

            @Override

            protected void initChannel(SocketChannel ch) throws Exception {

                /*

                 * 禁止堆类加载器进行缓存,他在基于 OSGI 的动态模块化编程中经常使用,由于 OSGI 可以进行热部署和热升级,当某个

                 * bundle

                 * 升级后,它对应的类加载器也将一起升级,因此在动态模块化的编程过程中,很少对类加载器进行缓存,因为他随时可能会发生变化.

                 */

                ch.pipeline().addLast(new ProtobufVarint32FrameDecoder());

                ch.pipeline().addLast(

                        new ProtobufDecoder(SubScriptRespProto.SubScriptResp

                                .getDefaultInstance()));

                ch.pipeline().addLast(

                        new ProtobufVarint32LengthFieldPrepender());

                ch.pipeline().addLast(new ProtobufEncoder());

                ch.pipeline().addLast(new SubReqClientHandler());

            }

        });

        // 发起异步链接操作

        ChannelFuture future;

        try {

            future = bootstrap.connect(host, port).sync();

            // 等待客户端链路关闭

            future.channel().closeFuture().sync();

        } catch (InterruptedException e) {

            e.printStackTrace();

        } finally {

            workGroup.shutdownGracefully();

        }

    }

    public static void main(String[] args) {

        new SubReqProtobufClient().connect("localhost", 9091);

    }

}

clientHandler

package protobuf.client.impl;

import io.netty.channel.ChannelHandlerAdapter;

import io.netty.channel.ChannelHandlerContext;

import object.server.impl.SubScriptReqProto;

public class SubReqClientHandler extends ChannelHandlerAdapter {

    @Override

    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)

            throws Exception {

        cause.printStackTrace();

        ctx.close();

    }

    @Override

    public void channelActive(ChannelHandlerContext ctx) throws Exception {

        try {

            SubScriptReqProto.SubScriptReq.Builder builder = SubScriptReqProto.SubScriptReq

                    .newBuilder();

            for (int i = 0; i < 100; i++) {

                builder.setSubReqID(999 + i);

                builder.setAddress("address" + i);

                builder.setProductName("productvalue" + i);

                builder.setUserName("userName" + i);

                ctx.writeAndFlush(builder.build());

            }

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

    @Override

    public void channelRead(ChannelHandlerContext ctx, Object msg)

            throws Exception {

        System.out.println("SubReqClientHandler : " + msg);

    }

    @Override

    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {

        ctx.flush();

    }

}

使用 ProtoBuf 的注意事项:

　　ProtobufDecode 只负责解码,它不支持半包读写,因此,在 protoBuf 前一定要一个能处理半包读写的处理器.他有三种方法可以选择:

  1. 使用 Netty 提供的 ProtobufVarint32FrameDecoder;
  2. 继承 Netty 提供的通用半包解码器 LengthFieldBasedFrameDecoder;
  3. 继承 ByteToMessageDecoder 类,自己处理半包消息

　　

以上内容出自 : <Netty 权威指南

>

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