Java基于ServletContextListener实现UDP监听

这篇文章主要介绍了Java基于ServletContextListener实现UDP监听,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

使用spring boot实现项目启动时的监听，

UDPListener

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

@WebListener
public class UDPListener implements ServletContextListener {

  public static final int MAX_UDP_DATA_SIZE = 4096;
  public static final int UDP_PORT = 26666;

  @Override
  public void contextInitialized(ServletContextEvent sce) {

    System.out.println("========UDPListener Initialized=========");
    try {
　　　　　　　// 启动一个线程，监听UDP数据报
      new Thread(new UDPProcess(UDP_PORT)).start();
    } catch (Exception e) {
      e.printStackTrace();
    }

  }

  class UDPProcess implements Runnable {
    DatagramSocket socket = null;

    public UDPProcess(final int port) throws SocketException {
      socket = new DatagramSocket(port);
    }

    @Override
    public void run() {
      // TODO Auto-generated method stub
      System.out.println("=======UDPProcess======");
      while (true) {
        byte[] buffer = new byte[MAX_UDP_DATA_SIZE];
        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
        try {
          socket.receive(packet);
          new Thread(new Process(packet)).start();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }

    }
  }

  class Process implements Runnable {

    public Process(DatagramPacket packet) throws UnsupportedEncodingException {
      // TODO Auto-generated constructor stub
      byte[] buffer = packet.getData();// 接收到的UDP信息，然后解码
      String srt1 = new String(buffer,"GBK").trim();
      String srt2 = new String(buffer, "UTF-8").trim();
      String srt3 = new String(buffer,"ISO-8859-1").trim();
      System.out.println("=======Process srt1 GBK======" + srt1);
      System.out.println("=======Process srt2 UTF-8======" + srt2);
      System.out.println("=======Process srt3 ISO-8859-1======" + srt3);
    }

    @Override
    public void run() {
      // TODO Auto-generated method stub
      System.out.println("====Process run=====");
    }
    
  }

  @Override
  public void contextDestroyed(ServletContextEvent sce) {
    System.out.println("========UDPListener Destroyed=========");
  }

}

DemoApplication

@SpringBootApplication
@ServletComponentScan 
public class DemoApplication {

  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }
}

@ServletComponentScan Servlet扫描，启动时把servlet、filter、listener自动扫描注入

UDP测试客户端（也可以用测试工具发送UDP包测试）：

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPClientTest {

  public static final String SERVER_HOSTNAME = "localhost";
  // 服务器端口
  public static final int SERVER_PORT = 26666;
  // 本地发送端口
  public static final int LOCAL_PORT = 8888;

  public static void main(String[] args) {
    try {
      // 1，创建udp服务。通过DatagramSocket对象。
      DatagramSocket socket = new DatagramSocket(LOCAL_PORT);
      // 2，确定数据，并封装成数据包。DatagramPacket(byte[] buf, int length, InetAddress
      // address, int port)
      byte[] buf = "你好，世界".getBytes();
      DatagramPacket dp = new DatagramPacket(buf, buf.length, InetAddress.getByName(SERVER_HOSTNAME),
          SERVER_PORT);
      // 3，通过socket服务，将已有的数据包发送出去。通过send方法。
      socket.send(dp);
      // 4，关闭资源。
      socket.close();
    } catch (IOException e) {
      e.printStackTrace();
    }
  }

}

结果：

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