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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