场景

在SpringBoot项目中需要对接三方系统，对接协议是TCP，需实现一个TCP客户端接收

服务端发送的数据并按照16进制进行解析数据，然后对数据进行过滤，将指定类型的数据

通过mybatis存储进mysql数据库中。并且当tcp服务端断连时，tcp客户端能定时检测并发起重连。

全流程效果

注：

博客：
霸道流氓气质的博客_CSDN博客-C#,架构之路,SpringBoot领域博主

实现

SpringBoot+Netty实现TCP客户端

本篇参考如下博客，在如下博客基础上进行修改

Springboot+Netty搭建基于TCP协议的客户端（二）:

https://www.cnblogs.com/haolb123/p/16553005.html

上面博客提供的示例代码

https://download.csdn.net/download/myyhtw/12369531

引入Netty的依赖

                            io.netty            netty-all

新建Netty的client类

package com.badao.demo.netty;import com.badao.demo.global.Global;import io.netty.bootstrap.Bootstrap;import io.netty.channel.Channel;import io.netty.channel.ChannelFuture;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;public class BootNettyClient { public void connect(int port, String host) throws Exception{          EventLoopGroup group = new NioEventLoopGroup();        try {                  Bootstrap bootstrap = new Bootstrap();         bootstrap = bootstrap.group(group);         bootstrap = bootstrap.channel(NioSocketChannel.class).option(ChannelOption.TCP_NODELAY, true);                  bootstrap = bootstrap.handler(new BootNettyChannelInitializer());            ChannelFuture future = bootstrap.connect(host, port).sync();   if(future.isSuccess()) {    //是否连接tcp成功    Global.getInstance().canTcpConnected = true;    Channel channel = future.channel();    String id = future.channel().id().toString();    BootNettyClientChannel bootNettyClientChannel = new BootNettyClientChannel();    bootNettyClientChannel.setChannel(channel);    bootNettyClientChannel.setCode("clientId:"+id);    BootNettyClientChannelCache.save("clientId:"+id, bootNettyClientChannel);    System.out.println("netty client start success="+id);        future.channel().closeFuture().sync();   }else{   }  } finally {      group.shutdownGracefully().sync();  } }}

注意这里的在连接成功之后的修改

新增了一个全局的单例变量类Global，用来作为断线重连的判断，后面后具体代码实现。

接着将clientId保存的实现，可以根据自己需要决定是否保留，不需要可删除，并且下面

第4条BootNettyClientChannel以及第5条BootNettyClientChannelCache也可做相应的删除或修改。

新建通道初始化

package com.badao.demo.netty;import io.netty.channel.Channel;import io.netty.channel.ChannelHandler;import io.netty.channel.ChannelInitializer;@ChannelHandler.Sharablepublic class BootNettyChannelInitializer extends ChannelInitializer { @Override protected void initChannel(Channel ch) {                ch.pipeline().addLast(new BootNettyChannelInboundHandlerAdapter()); }}

注意与原有不一样的是这里删掉了自定义解码器的实现

这里根据自己实际情况决定是否保留以及格式，否则会提示

String cannot be cast to io.netty.buffer.ByteBuf

新建通道对象

package com.badao.demo.netty;import io.netty.channel.Channel;public class BootNettyClientChannel { // 连接客户端唯一的code private String code; // 客户端最新发送的消息内容 private String last_data; private transient volatile Channel channel; public String getCode() {  return code; } public void setCode(String code) {  this.code = code; } public Channel getChannel() {  return channel; } public void setChannel(Channel channel) {  this.channel = channel; } public String getLast_data() {  return last_data; } public void setLast_data(String last_data) {  this.last_data = last_data; }}

新建保存ClientChannel的Cache类

package com.badao.demo.netty;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;public class BootNettyClientChannelCache {    public static volatile Map channelMapCache = new ConcurrentHashMap();    public static void add(String code, BootNettyClientChannel channel){     channelMapCache.put(code,channel);    }    public static BootNettyClientChannel get(String code){        return channelMapCache.get(code);    }    public static void remove(String code){     channelMapCache.remove(code);    }    public static void save(String code, BootNettyClientChannel channel) {        if(channelMapCache.get(code) == null) {            add(code,channel);        }    }}

最重要的是新建客户端I/O数据读写处理类

package com.badao.demo.netty;import com.badao.demo.entity.BusStallProptection;import com.badao.demo.entity.StallVo;import com.badao.demo.global.Global;import com.badao.demo.mapper.BusStallProptectionMapper;import io.netty.buffer.ByteBuf;import io.netty.channel.ChannelHandler;import io.netty.channel.ChannelHandlerContext;import io.netty.channel.ChannelInboundHandlerAdapter;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import javax.annotation.PostConstruct;import java.io.IOException;import java.net.InetSocketAddress;import java.util.Date;@ChannelHandler.Sharable@Componentpublic class BootNettyChannelInboundHandlerAdapter extends ChannelInboundHandlerAdapter{    public static BootNettyChannelInboundHandlerAdapter bootNettyChannelInboundHandlerAdapter;    //1.正常注入[记得主类也需要使用@Component注解]    @Autowired    BusStallProptectionMapper busStallProptectionMapper;    //2.初始化构造方法一定要有    public BootNettyChannelInboundHandlerAdapter(){    }    //3.容器初始化的时候进行执行-这里是重点    @PostConstruct    public void init() {        bootNettyChannelInboundHandlerAdapter = this;        bootNettyChannelInboundHandlerAdapter.busStallProptectionMapper = this.busStallProptectionMapper;    }        @Override    public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {        if(msg == null){            return;        }        ByteBuf buf = (ByteBuf) msg;        byte[] bytes = new byte[buf.readableBytes()];        // 复制内容到字节数组bytes        buf.readBytes(bytes);        // 将接收到的数据转为字符串，此字符串就是客户端发送的字符串        String receiveStr = NettyConnectHelper.receiveHexToString(bytes);        StallVo stallVo = NettyConnectHelper.receiveHexToObj(bytes);        BootNettyClientChannel bootNettyClientChannel = BootNettyClientChannelCache.get("clientId:"+ctx.channel().id().toString());        if(bootNettyClientChannel != null){            //判断指定状态的数据进行处理            if(Global.getInstance().abnormalCarStatusList.contains(stallVo.getCarStatus())){                BusStallProptection busStallProptection = BusStallProptection.builder()                        .carNumber(stallVo.getCarNumber())                        .carState(stallVo.getCarStatus())                        .stallScope(stallVo.getAreaNumber())                        .rawData(receiveStr)                        .uploadTime(new Date())                        .build();                //插入数据库                bootNettyChannelInboundHandlerAdapter.busStallProptectionMapper.insert(busStallProptection);            }            bootNettyClientChannel.setLast_data(msg.toString());        }    }        @Override    public void channelReadComplete(ChannelHandlerContext ctx) throws IOException {     ctx.flush();    }        @Override    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws IOException {     System.out.println("exceptionCaught");        cause.printStackTrace();        ctx.close();//抛出异常，断开与客户端的连接    }        @Override    public void channelActive(ChannelHandlerContext ctx) throws Exception, IOException {        super.channelActive(ctx);        InetSocketAddress inSocket = (InetSocketAddress) ctx.channel().remoteAddress();        String clientIp = inSocket.getAddress().getHostAddress();        System.out.println(clientIp);    }        @Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception, IOException {        super.channelInactive(ctx);        InetSocketAddress inSocket = (InetSocketAddress) ctx.channel().remoteAddress();        String clientIp = inSocket.getAddress().getHostAddress();        ctx.close(); //断开连接时，必须关闭，否则造成资源浪费        System.out.println("channelInactive:"+clientIp);        Global.getInstance().canTcpConnected = false;    }}

这里做的修改较多主要是修改channelRead从服务端收到新的数据时的回调方法

会将数据进行按照16进制读取和解析为字符串，并作为对接的原始数据进行存储。

还会将数据按照16进制解析并获取对应位的字符并赋值到对象保存到数据库。

其中用到的相关工具类方法，又封装了一个NettyConnectHelper

其中包含用来发起连接以及16进制解析和转换对象的相关方法

package com.badao.demo.netty;import com.badao.demo.entity.StallVo;public  class NettyConnectHelper {        public static void doConnect(){        try {                        new BootNettyClient().connect(8600, "127.0.0.1");        }catch (Exception exception){            System.out.println("tcp连接异常");        }    }        public  static String receiveHexToString(byte[] by) {        try {            String str = bytes2Str(by);            str = str.toUpperCase();            return str;        } catch (Exception ex) {            ex.printStackTrace();            System.out.println("接收字节数据并转为16进制字符串异常");        }        return null;    }        public static String bytes2Str(byte[] src){        StringBuilder stringBuilder = new StringBuilder("");        if (src == null || src.length <= 0) {            return null;        }        for (int i = 0; i < src.length; i++) {            if(i>0){                stringBuilder.append(" ");            }            int v = src[i] & 0xFF;            String hv = Integer.toHexString(v);            if (hv.length() < 2) {                stringBuilder.append(0);            }            stringBuilder.append(hv);        }        return stringBuilder.toString();    }        public static String byte2Str(byte src){        StringBuilder stringBuilder = new StringBuilder("");        int v = src & 0xFF;        String hv = Integer.toHexString(v);        if (hv.length() < 2) {            stringBuilder.append(0);        }        stringBuilder.append(hv.toUpperCase());        return stringBuilder.toString();    }        public static StallVo receiveHexToObj(byte[] by) {        try {            StallVo stallVo = bytes2Obj(by);            return stallVo;        } catch (Exception ex) {            ex.printStackTrace();            System.out.println("接收字节数据并转为对象异常");        }        return null;    }        public static StallVo bytes2Obj(byte[] src){        if (src == null || src.length <= 0) {            return null;        }        //依据约定，第一位为区域编号；第四位为车辆状态；第五位为车辆编号        StallVo stallVo = StallVo.builder()                .areaNumber(byte2Str(src[0]))                .carStatus(byte2Str(src[3]))                .carNumber(byte2Str(src[4]))                .build();        return stallVo;    }}

这里跟业务相关挺多，对象属性映射的都是依据对接时的约定。

这里的对象StallVo

package com.badao.demo.entity;import lombok.Builder;import lombok.Data;@Data@Builderpublic class StallVo {    //区域编号    private String areaNumber;    //车辆状态    private String carStatus;    //车辆编号    private String carNumber;}

继续上面的读的处理类

if(Global.getInstance().abnormalCarStatusList.contains(stallVo.getCarStatus()))

这里是业务需要，根据传输的数据进行判断，指定位的数据是否为需要的类型数据，只对需要的数据进行存储。

下面附全局单例类Global

package com.badao.demo.global;import com.badao.demo.enums.CarStatus;import java.util.ArrayList;import java.util.List;public class Global {    //标识当前是否已经连接TCP    public  boolean canTcpConnected = false;    //过滤tcp数据，需要的数据类型的枚举变量的list    public List abnormalCarStatusList = new ArrayList()    {        {            add(CarStatus.OverSpeed.getCode());            add(CarStatus.EmergStop.getCode());            add(CarStatus.StallProtected.getCode());        }    };    private static final Global _global = new Global();    private Global(){};    public static Global getInstance(){        return _global;    }}

关于单例模式的实现可参考

设计模式-单例模式-饿汉式单例模式、懒汉式单例模式、静态内部类在Java中的使用示例:

设计模式-单例模式-饿汉式单例模式、懒汉式单例模式、静态内部类在Java中的使用示例_霸道流氓气质的博客-CSDN博客

其中Global中保存的list是枚举类的相关字段属性

package com.badao.demo.enums;public enum CarStatus{    NormalCar("00", "没有车辆通过或车辆速度正常"), OverSpeed("01", "车辆超速行驶"),EmergStop("02", "车辆急停"), StallProtected("03", "车辆失速保护");    private final String code;    private final String info;    CarStatus(String code, String info)    {        this.code = code;        this.info = info;    }    public String getCode()    {        return code;    }    public String getInfo()    {        return info;    }}

继续上面在解析数据并判断是需要的类型之后，就是封装到存储数据库的相关实体并插入到mysql。

附BusStallProptection

package com.badao.demo.entity;import lombok.Builder;import lombok.Data;import java.io.Serializable;import java.util.Date;@Data@Builderpublic class BusStallProptection implements Serializable {    private Integer id;    private String carNumber;    private String carState;    private String stallScope;    private String rawData;    private Date uploadTime;}

封装完之后实现调用mapper的方法插入到数据库。

Netty的I/O数据读写处理类BootNettyChannelInboundHandlerAdapter中注入Mapper的方式

I/O数据读写处理类BootNettyChannelInboundHandlerAdapter添加注解@Component

@ChannelHandler.Sharable@Componentpublic class BootNettyChannelInboundHandlerAdapter extends ChannelInboundHandlerAdapter{

然后正常注入mapper或service

    //1.正常注入[记得主类也需要使用@Component注解]    @Autowired    BusStallProptectionMapper busStallProptectionMapper;

然后新增初始化构造方法

    //2.初始化构造方法一定要有    public BootNettyChannelInboundHandlerAdapter(){    }

然后容器初始化时执行如下

    //3.容器初始化的时候进行执行-这里是重点    @PostConstruct    public void init() {        bootNettyChannelInboundHandlerAdapter = this;        bootNettyChannelInboundHandlerAdapter.busStallProptectionMapper = this.busStallProptectionMapper;    }

前面要声明static变量

public static BootNettyChannelInboundHandlerAdapter bootNettyChannelInboundHandlerAdapter;

然后在使用时就可以

bootNettyChannelInboundHandlerAdapter.busStallProptectionMapper.insert(busStallProptection);

修改SpringBoot的启动类，使Netty项目启动后进行TCP连接

package com.badao.demo;import com.badao.demo.netty.NettyConnectHelper;import org.mybatis.spring.annotation.MapperScan;import org.springframework.boot.CommandLineRunner;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@MapperScan("com.badao.demo.mapper")@SpringBootApplicationpublic class DemoApplication implements CommandLineRunner {    public static void main(String[] args) {        SpringApplication application = new SpringApplication(DemoApplication.class);        application.run(args);    }    @Override    public void run(String... args) {        //如果需要项目一启动就连接则执行，否则通过定时任务执行        NettyConnectHelper.doConnect();    }}

这里将发起连接的操作封装到工具类方法中，并在方法中添加try-catch，避免连接不上tcp导致无法启动。

SpringBoot中进行TCP客户端断线检测与自动重连。

这里需要TCP的客户端在断线之后能自动发起重连，且不需重启SpringBoot，所以这里需要借助定时任务的

实现。

新建Task类并进行定时任务实现

package com.badao.demo.task;import com.badao.demo.global.Global;import com.badao.demo.netty.NettyConnectHelper;import org.springframework.scheduling.annotation.EnableScheduling;import org.springframework.scheduling.annotation.Scheduled;import org.springframework.stereotype.Component;@Component@EnableSchedulingpublic class CheckTcpConnectTask {    @Scheduled(cron = "0/10 * * * * ? ")    public void  checkReconnectTcpServer(){        System.out.println("发起重连检测");        if(!Global.getInstance().canTcpConnected){            //进行连接            System.out.println("执行连接");            NettyConnectHelper.doConnect();        }    }}

这里是10秒检测一次前面定义的全局变量，如果未连接则调用发起连接的方法。

该变量默认为false，在建立连接的回调方法BootNettyClient中连接服务端之后将其赋值

为true。

   ChannelFuture future = bootstrap.connect(host, port).sync();   if(future.isSuccess()) {    //是否连接tcp成功    Global.getInstance().canTcpConnected = true;

并在断连的回调BootNettyChannelInboundHandlerAdapter的channelInactive赋值为false

    @Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception, IOException {        super.channelInactive(ctx);        InetSocketAddress inSocket = (InetSocketAddress) ctx.channel().remoteAddress();        String clientIp = inSocket.getAddress().getHostAddress();        ctx.close(); //断开连接时，必须关闭，否则造成资源浪费        System.out.println("channelInactive:"+clientIp);        Global.getInstance().canTcpConnected = false;    }