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>