import java.util.TimerTask;
import javax.servlet.ServletContext;

public class MyTask extends TimerTask{
  private ServletContext context = null;
  
  public CleanTpIpTask(ServletContext servletContext) {
    this.context = servletContext;
  }
  @Override
  public void run() {
    //定時任務(wù)邏輯代碼
  }
}

import java.util.Calendar;
import java.util.Date;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyTaskListener implements ServletContextListener {
  private java.util.Timer timer = null; 
  MyTask myTask = null;
  public void contextDestroyed(ServletContextEvent arg0) {
    timer.cancel();
    
  }
  public void contextInitialized(ServletContextEvent arg0) {
    Calendar c = Calendar.getInstance();
    int year = c.get(Calendar.YEAR);
    int month = c.get(Calendar.MONTH);
    int day = c.get(Calendar.DAY_OF_MONTH);
    c.set(year, month, day, 3, 0, 0);//項目啟動當(dāng)天凌晨3點執(zhí)行1次，如果已經(jīng)超過凌晨3點，立刻執(zhí)行
    Date date = c.getTime();
    timer = new java.util.Timer(true); 
    
    int period = 24 * 60 * 60 * 1000;//執(zhí)行間隔
    if(myTask==null){
      myTask = new MyTask(arg0.getServletContext());
      timer.schedule(new MyTask(arg0.getServletContext()), date, period);　　
      //timer.schedule(new CleanTpIpTask(arg0.getServletContext()), date);//只執(zhí)行1次 
      //timer.schedule(new CleanTpIpTask(arg0.getServletContext()), 0, period);//項目啟動立刻執(zhí)行，每隔period 毫秒執(zhí)行1次

    }
  }
}

 <listener>
   <listener-class>webservice.MyTaskListener</listener-class>
 </listener>