用Java定的定時任務，有的時候在執行一些后臺任務時很有用

listenBean.java

import javax.servlet.*;
import java.util.*;
public class listenerBean implements ServletContextListener {
??private java.util.Timer timer = null;
??public void contextInitialized(ServletContextEvent event) {
??timer = new Timer(true);
??//定時器已啟動
??timer.schedule(new MyTask(), 0, (long) 1000*60);//定時1分鐘
??//已經添加任務調度表
?}
?public void contextDestroyed(ServletContextEvent event) {
??timer.cancel();
??//定時器銷毀
?}
}
class MyTask extends TimerTask {
?private static boolean isRunning = false;
?public void run() {
??if (!isRunning) {
???isRunning = true;
???//開始執行任務
???//ToDo ....
???//執行任務完成
???isRunning = false;
??} else {
???//上一次任務執行還未結束
??}
?}
}

web.xml

<web-app>
?<listener>
??? <listener-class>listenerBean</listener-class>
</listener>
</web-app>