监听器实现定时任务（java定时器）

参考：https://blog.csdn.net/u011110383/article/details/73530505

java代码：
import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;

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

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.ibm.icu.util.Calendar;

public class TimerListener implements ServletContextListener {

private Timer timer=null;
private ServletContext context=null;

/**
* 启动任务
*/
public void contextInitialized(ServletContextEvent event){
this.context =event.getServletContext();
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY,18);
calendar.set(Calendar.MINUTE,38);
calendar.set(Calendar.SECOND,0);
Date time =calendar.getTime();

long period_day=24*60*60*1000;

//如果第一次执行时间小于当前时间，则将第一次执行任务的时间加一天。
if(time.before(new Date())){
time=this.addDay(time,1);
}

context.log(“定时器启动”);
timer=new Timer(true);
timer.scheduleAtFixedRate(new MyTask(this.context), time, period_day);
}

/**
* 销毁任务
*/
public void contextDestroyed(ServletContextEvent event) {
if (timer != null) {
timer.cancel();
event.getServletContext().log(“定时器销毁”);
}
}

/**
 * 获取时间
 * @param date
 * @param num
 * @return
 */
public Date addDay(Date date, int num){
 Calendar startDT =Calendar.getInstance();
 startDT.setTime(date);
 startDT.add(Calendar.DAY_OF_MONTH, num);
 return startDT.getTime();
}


//内部类定时任务
private static class MyTask extends TimerTask{
 private ServletContext context=null;

 public MyTask(ServletContext context){
  this.context=context;
 }
 public void run() {
  try {
   WebApplicationContext webContext =WebApplicationContextUtils.getRequiredWebApplicationContext(this.context);
   context.log("开始执行任务");
   //获取spring容器管理的javaBean
   AlarmDAO alarmDAO =(AlarmDAO) webContext.getBean("com.abchina.plantix.alarm.dao.AlarmDAO");
   alarmDAO.deleteAlarm();
      alarmDAO.insertCreditLimitAlarm();
   context.log("任务执行结束");
  } catch (Exception e) {
   e.printStackTrace();
  }

 }
}

}

web-xml的监听器配置：
<listener>
<listener-class>
com.abchina.plantix.alarm.dao.TimerListener
</listener-class>
</listener>