Google Protobuf在Netty中的使用

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Google Protobuf在Netty中的使用

程序代码来自于《Netty权威指南》第8章，已经加了注释，不过需要注意的是，使用的proto源代码是在Google Protobuf入门与使用中生成的，关于protobuf代码自动生成工具的使用可以参考这篇文章。

例子中，通过×××ProtobufVarint32FrameDecoder和编码器ProtobufVarint32LengthFieldPrepender的使用已经解决了半包问题，测试时可以把其注释掉，这样就可以演示Netty中使用Protobuf出现的TCP粘包问题。

同时，通过protobuf的使用，也可以深刻感受到，其在Netty中的使用确实非常简单，编解码、半包问题，只需要添加相关的处理器即可，而且它可以方便地实现跨语言的远程服务调用。（protobuf本身提供了对不同语言的支持）

但其实在使用时会发现有一个问题，就是编解码的对象是需要使用其生成的特定的proto对象来进行操作的，也就是说，需要编写.proto文件，再通过protoc来生成相应语言的代码文件，显然这样做还是会有些麻烦（虽然其实也还好，不算麻烦），有没有方便点的方法呢？后面通过protostuff的使用即可解决这个问题。

服务端

SubReqServer.java

package cn.xpleaf.subscribe;

import cn.xpleaf.protobuf.SubscribeReqProto;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
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;

public class SubReqServer {
    public void bind(int port) throws Exception {
        // 配置服务端的NIO线程组
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();

        try {
            ServerBootstrap b = new ServerBootstrap();
            b.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, 1024)
                // 添加日志处理器
                .handler(new LoggingHandler(LogLevel.INFO))
                .childHandler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        // 添加ProtobufVarint32FrameDecoder，主要用于Protobuf的半包处理
                        ch.pipeline().addLast(new ProtobufVarint32FrameDecoder());
                        // 添加ProtobufDecoder×××，它的参数是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
                        // 无法判断出要解码的目标类型信息的（服务端需要解析的是客户端请求，所以是Req）
                        ch.pipeline().addLast(new ProtobufDecoder(SubscribeReqProto.SubscribeReq.getDefaultInstance()));
                        /**
                         * 来自源码的代码注释，用于Protobuf的半包处理
                         * * An encoder that prepends the the Google Protocol Buffers
                         * <a href="https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints">Base
                         * 128 Varints</a> integer length field. For example:
                         * <pre>
                         * BEFORE ENCODE (300 bytes)       AFTER ENCODE (302 bytes)
                         * +---------------+               +--------+---------------+
                         * | Protobuf Data |-------------->| Length | Protobuf Data |
                         * |  (300 bytes)  |               | 0xAC02 |  (300 bytes)  |
                         * +---------------+               +--------+---------------+
                         * </pre> *
                         */
                        ch.pipeline().addLast(new ProtobufVarint32LengthFieldPrepender());
                        // 添加ProtobufEncoder编码器，这样就不需要对SubscribeResp进行手工编码
                        ch.pipeline().addLast(new ProtobufEncoder());
                        // 添加业务处理handler
                        ch.pipeline().addLast(new SubReqServerHandler());
                    }
                });

            // 绑定端口，同步等待成功
            ChannelFuture f = b.bind(port).sync();

            // 等待服务端监听端口关闭
            f.channel().closeFuture().sync();
        } finally {
            // 优雅退出，释放线程池资源
            bossGroup.shutdownGracefully();
            workerGroup.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8080;
        if(args != null && args.length > 0) {
            try {
                port = Integer.valueOf(port);
            } catch (NumberFormatException e) {
                // TODO: handle exception
            }
        }
        new SubReqServer().bind(port);
    }
}

SubReqServerHandler.java

package cn.xpleaf.subscribe;

import cn.xpleaf.protobuf.SubscribeReqProto;
import cn.xpleaf.protobuf.SubscribeRespProto;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class SubReqServerHandler extends ChannelInboundHandlerAdapter {

    /**
     * 由于ProtobufDecoder已经对消息进行了自动解码，因此接收到的订购请求消息可以直接使用
     * 对用户名进行校验，校验通过后构造应答消息返回给客户端，由于使用了ProtobufEncoder，
     * 所以不需要对SubscribeRespProto.SubscribeResp进行手工编码
     */
    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        SubscribeReqProto.SubscribeReq req = (SubscribeReqProto.SubscribeReq)msg;
        String username = req.getUserName();
        if("xpleaf".equalsIgnoreCase(username)) {
            System.out.println("Service accept client subscribe req : [" + req.toString() + "]");
            ctx.writeAndFlush(resp(req.getSubReqID()));
        }
    }

    /**
     * 构建SubscribeRespProto.SubscribeResp对象
     * @param subReqID
     * @return
     */
    private SubscribeRespProto.SubscribeResp resp(int subReqID) {
        SubscribeRespProto.SubscribeResp.Builder builder = SubscribeRespProto.SubscribeResp.newBuilder();
        builder.setSubReqID(subReqID);
        builder.setRespCode(0);
        builder.setDesc("Netty book order succeed, 3 days later, sent to the designated address");
        return builder.build();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        // 发生异常，关闭链路
        ctx.close();
    }
}

客户端

SubReqClient.java

package cn.xpleaf.subscribe;

import cn.xpleaf.protobuf.SubscribeRespProto;
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
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.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;

public class SubReqClient {
    public void connect(String host, int port) throws Exception {
        // 配置客户端NIO线程组
        EventLoopGroup group = new NioEventLoopGroup();
        try {
            Bootstrap b = new Bootstrap();
            b.group(group).channel(NioSocketChannel.class)
                .option(ChannelOption.TCP_NODELAY, true)
                // 设置TCP连接超时时间
                .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, 3000)
                .handler(new ChannelInitializer<SocketChannel>() {

                    @Override
                    protected void initChannel(SocketChannel ch) throws Exception {
                        // 添加ProtobufVarint32FrameDecoder，主要用于Protobuf的半包处理
                        ch.pipeline().addLast(new ProtobufVarint32FrameDecoder());
                        // 添加ProtobufDecoder×××，它的参数是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
                        // 无法判断出要解码的目标类型信息的（客户端需要解析的是服务端请求，所以是Resp）
                        ch.pipeline().addLast(new ProtobufDecoder(SubscribeRespProto.SubscribeResp.getDefaultInstance()));
                        /**
                         * 来自源码的代码注释，用于Protobuf的半包处理
                         * * An encoder that prepends the the Google Protocol Buffers
                         * <a href="https://developers.google.com/protocol-buffers/docs/encoding?csw=1#varints">Base
                         * 128 Varints</a> integer length field. For example:
                         * <pre>
                         * BEFORE ENCODE (300 bytes)       AFTER ENCODE (302 bytes)
                         * +---------------+               +--------+---------------+
                         * | Protobuf Data |-------------->| Length | Protobuf Data |
                         * |  (300 bytes)  |               | 0xAC02 |  (300 bytes)  |
                         * +---------------+               +--------+---------------+
                         * </pre> *
                         */
                        ch.pipeline().addLast(new ProtobufVarint32LengthFieldPrepender());
                        // 添加ProtobufEncoder编码器，这样就不需要对SubscribeResp进行手工编码
                        ch.pipeline().addLast(new ProtobufEncoder());
                        // 添加业务处理handler
                        ch.pipeline().addLast(new SubReqClientHandler());
                    }
                });
            // 发起异步连接操作
            ChannelFuture f = b.connect(host, port).sync();

            // 等待客户端链路关闭
            f.channel().closeFuture().sync();
        } finally {
            // 优雅退出，释放NIO线程组
            group.shutdownGracefully();
        }
    }

    public static void main(String[] args) throws Exception {
        int port = 8080;
        if(args != null && args.length > 0) {
            try {
                port = Integer.valueOf(port);
            } catch (NumberFormatException e) {
                // 采用默认值
            }
        }
        new SubReqClient().connect("localhost", port);
    }
}

SubReqClientHandler.java

package cn.xpleaf.subscribe;

import java.util.ArrayList;
import java.util.List;

import cn.xpleaf.protobuf.SubscribeReqProto;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;

public class SubReqClientHandler extends ChannelInboundHandlerAdapter {

    @Override
    public void channelActive(ChannelHandlerContext ctx) {
        for(int i = 0; i < 10; i++) {
            ctx.write(subReq(i));
        }
        ctx.flush();
    }

    /**
     * 构建SubscribeReqProto.SubscribeReq对象
     * @param i
     * @return
     */
    private SubscribeReqProto.SubscribeReq subReq(int i) {
        SubscribeReqProto.SubscribeReq.Builder builder = SubscribeReqProto.SubscribeReq.newBuilder();
        builder.setSubReqID(i);
        builder.setUserName("xpleaf");
        builder.setProductName("Netty Book For Protobuf");
        List<String> address = new ArrayList<>();
        address.add("NanJing YuHuaTai");
        address.add("BeiJing LiuLiChange");
        address.add("ShenZhen HongShuLin");
        builder.addAllAddress(address);
        return builder.build();
    }

    @Override
    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
        System.out.println("Service accept server subscribe response : [" + msg + "]");
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {
        ctx.flush();
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
        cause.printStackTrace();
        ctx.close();
    }
}

测试

服务端输出如下：

Service accept client subscribe req : [subReqID: 0
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 1
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 2
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 3
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 4
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 5
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 6
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 7
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 8
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]
Service accept client subscribe req : [subReqID: 9
userName: "xpleaf"
productName: "Netty Book For Protobuf"
address: "NanJing YuHuaTai"
address: "BeiJing LiuLiChange"
address: "ShenZhen HongShuLin"
]

客户端输出如下：

Service accept server subscribe response : [subReqID: 0
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 1
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 2
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 3
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 4
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 5
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 6
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 7
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 8
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]
Service accept server subscribe response : [subReqID: 9
respCode: 0
desc: "Netty book order succeed, 3 days later, sent to the designated address"
]

来源：51CTO

作者：xpleaf

链接：https://blog.51cto.com/xpleaf/2071715