springboot 开启一个udp服务端。

待我称王封你为后i 2022-10-23 01:59 162阅读 0赞

## 写在前面 ##

udp客户端本片文章暂且不提。本篇文章重点介绍一下服务端的创建，以及遇到的坑。

## 创建UDP服务端 ##

创建一个线程来启动这个服务端，然后监听26660这个端口。

import com.cdwuyue.udp.UDPProcesService;
    import org.springframework.stereotype.Component;
    
    import javax.annotation.Resource;
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    import java.io.IOException;
    import java.io.UnsupportedEncodingException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.SocketException;
    import java.util.logging.Logger;
    
    /*
     * UDP服务器端
     */
    //@WebListener
    //为了注入Service，使用Component
    @Component
    public class UDPServer implements ServletContextListener {
        public static Logger logger = Logger.getLogger(UDPServer.class.getName());
        public static final int MAX_UDP_DATA_SIZE = 4096;
        public static final int UDP_PORT = 26660;//UDP监听端口
        public static DatagramPacket packet = null;
        public static DatagramSocket socket = null;
    
        @Resource
        private UDPProcesService udpProcesService;
    
        @Override
        public void contextInitialized(ServletContextEvent sce) {
            try {
                // 启动一个线程，监听UDP数据报
                logger.info("========启动一个线程，监听UDP数据报.PORT:" + UDP_PORT + "=========");
                new Thread(new UDPProcess(UDP_PORT)).start();
                logger.info("========  创建完成    =========");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
        class UDPProcess implements Runnable {
    
            public UDPProcess(final int port) throws SocketException {
                //创建服务器端DatagramSocket，指定端口
                socket = new DatagramSocket(port);
            }
    
            @Override
            public void run() {
                while (true) {
                    byte[] buffer = new byte[MAX_UDP_DATA_SIZE];
                    packet = new DatagramPacket(buffer, buffer.length);
                    try {
                        socket.receive(packet);
                        new Thread(new Process(packet)).start();
                    } catch (IOException | InterruptedException e) {
                        e.printStackTrace();
                    }
                }
    
            }
    
        }
    
        class Process implements Runnable {
            public Process(DatagramPacket packet) throws IOException, InterruptedException {
                byte[] buffer = packet.getData();// 接收到的UDP信息，然后解码
                String srt2 = new String(buffer, "GBK").trim();
                //todo 保存数据
                udpProcesService.process(srt2.trim());
            }
    
            @Override
            public void run() {
    
            }
    
        }
    
        @Override
        public void contextDestroyed(ServletContextEvent sce) {
            logger.info("========UDPListener摧毁=========");
        }
    
    }

@Component
    public class UDPProcesService {
    
    
        private static final Logger LOGGER = LoggerFactory.getLogger(UDPProcesService.class);
    
    
        //UDP接收验
        public  static void process(String msg) throws IOException, InterruptedException {
            Map<String,String> kafkaModel1 =  ApplicationContextProvider.getBean("kafkaModel1", ConcurrentHashMap.class);//获取所有站点对应的机构id
    
            LOGGER.info("UDP接收消息"+msg);
        }
    }

## 坑一 ##

**注意我这里是项目启动时注入了kafkaModel1这个bean的，这时候启动时，会报空指针异常，因为kafkaModel1还没有注入，而此时线程已经创建完成了。**

所以需要先注入bean，再启动线程。

因此将UDPServer实现ApplicationRunner，项目启动后再启动线程

import com.cdwuyue.udp.UDPProcesService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.boot.ApplicationArguments;
    import org.springframework.boot.ApplicationRunner;
    import org.springframework.stereotype.Component;
    
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    import java.io.IOException;
    import java.net.DatagramPacket;
    import java.net.DatagramSocket;
    import java.net.SocketException;
    import java.util.logging.Logger;
    
    /*
     * UDP服务器端
     */
    //@WebListener
    //为了注入Service，使用Component
    @Component
    public class UDPServer implements ApplicationRunner, ServletContextListener {
        public static Logger logger = Logger.getLogger(UDPServer.class.getName());
        public static final int MAX_UDP_DATA_SIZE = 4096;
        public static final int UDP_PORT = 26660;//UDP监听端口
        public static DatagramPacket packet = null;
        public static DatagramSocket socket = null;
    
        @Autowired
        private UDPProcesService udpProcesService;
    
        @Override
        public void run(ApplicationArguments args) throws Exception {
            try {
                // 启动一个线程，监听UDP数据报
                logger.info("========启动一个线程，监听UDP数据报.PORT:" + UDP_PORT + "=========");
    
                new Thread(new UDPProcess(UDP_PORT)).start();
                logger.info("========  创建完成    =========");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    
        class UDPProcess implements Runnable {
    
            public UDPProcess(final int port) throws SocketException, InterruptedException {
                //创建服务器端DatagramSocket，指定端口
                socket = new DatagramSocket(port);
            }
    
            @Override
            public void run() {
                while (true) {
                    byte[] buffer = new byte[MAX_UDP_DATA_SIZE];
                    packet = new DatagramPacket(buffer, buffer.length);
                    try {
                        socket.receive(packet);
                        new Thread(new Process(packet)).start();
                    } catch (IOException | InterruptedException e) {
                        e.printStackTrace();
                    }
                }
    
            }
    
        }
    
        class Process implements Runnable {
            public Process(DatagramPacket packet) throws IOException, InterruptedException {
                byte[] buffer = packet.getData();// 接收到的UDP信息，然后解码
                String srt2 = new String(buffer, "GBK").trim();
                //todo 保存数据
                udpProcesService.process(srt2.trim());
            }
    
            @Override
            public void run() {
    
            }
    
        }
    
        @Override
        public void contextDestroyed(ServletContextEvent sce) {
            logger.info("========UDPListener摧毁=========");
        }
    
    }

那么上述是第一个坑。

## 坑二 ##

就是使用docker部署。

在开放了云服务器端口，防火墙端口的情况下，docker启动容器时也要映射端口。

docker run -di --name=xinda -p xxxx:xxxx -p 26660:26660/udp 镜像名