java中服务器启动时，执行定时任务

package com.ripsoft.util;

import java.util.Calendar;
import java.util.Timer;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class TimerListener implements ServletContextListener{
    private Timer timer = null;  
      
    @Override  
    public void contextInitialized(ServletContextEvent event) {  
        timer = new Timer(true);  
        event.getServletContext().log("定时器已启动");  
       
      //设置执行时间
        Calendar calendar = Calendar.getInstance();
        int year = calendar.get(Calendar.YEAR);
        int month = calendar.get(Calendar.MONTH);
        int day = calendar.get(Calendar.DAY_OF_MONTH);//每天
        //定制每天的11:00:00执行
        calendar.set(year, month, day, 11, 00, 00);
        java.util.Date date = calendar.getTime();
        int period = 30 * 1000;
        //每天的date时刻执行TestTask，每隔30秒重复执行
        timer.schedule(new TestTask(), date, period);
        //每天的date时刻执行TestTask, 仅执行一次
        //timer.schedule(new TestTask(), date);
    }  
  
    @Override  
    public void contextDestroyed(ServletContextEvent event) {  
        if (timer != null) {  
            timer.cancel();  
            event.getServletContext().log("定时器销毁");  
        }  
    }  
}

package com.ripsoft.util;

import java.util.TimerTask;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class TestTask extends TimerTask{
    protected final Log logger = LogFactory.getLog(getClass());  
      
    private static boolean isRunning = false;  
  
    @Override  
    public void run() {  
        if (!isRunning) {  
            isRunning = true;  
            logger.info("开始执行任务。");  
  
            int i = 0;  
            while (i++ < 10) {  
                logger.info("已完成任务的" + i + "/" + 10);  
            }  
  
            isRunning = false;  
            logger.info("任务执行结束。");  
  
        } else {  
            logger.info("上一次任务执行还未结束，本次任务不能执行。");  
        }  
  
    }  
}

1.TestTimerListener.java执行定时任务，实现servlet的ServletContextListener接口，当服务器启动时开始执行TestTask任务

2.想要任务在服务器启动时定时执行，就要借助监听实现需要在web.xml中做如下配置

    <listener>
        <listener-class>com.ripsoft.util.TimerListener</listener-class>
    </listener>