怎么在Web程序中实现定时运行的功能 _Web前端

如何在Web程序中实现定时运行的功能？

定时器在Web中的应用

关键字: java定时器在web中的应用

在web中,定时器的启动一般随web server的启动而启动,一般有两种方法.?

方法一：在web.xml里配置一个Servlet，并设置其随web server的启动而启动。然后在该Servlet的init()方法里启动定时器，在destory()方法里销毁定时器。?
方法二：在web.xml里配置一个Listener,然后在该Listener的初始化方法里启动定时器，在其销毁的方法朝左销毁定时器。?

在servlet中启动定时器?

Xml代码?

import?java.io.IOException;??????
import?java.util.Timer;??????
import?javax.servlet.RequestDispatcher;??????
import?javax.servlet.ServletContext;??????
import?javax.servlet.ServletException;??????
import?javax.servlet.http.HttpServlet;??????
import?javax.servlet.http.HttpServletRequest;??????
import?javax.servlet.http.HttpServletResponse;??????
?????
import?org.apache.commons.lang.StringUtils;??????
?????
public?class?ConvergeDataServlet?extends?HttpServlet?{??????
?????
????private?static?final?long?serialVersionUID?=?1L;??????
?????
????private?Timer?timer1?=?null;??????
??????????
????private?Task?task1;??????
??????????
????/**?????
?????*?Constructor?of?the?object.?????
?????*/?????
????public?ConvergeDataServlet()?{??????
????????super();??????
????}??????
?????
????/**?????
?????*?Destruction?of?the?servlet.???
????
?????*/?????
????public?void?destroy()?{??????
????????super.destroy();???????
????????if(timer1!=null){??????
????????????timer1.cancel();??????
????????}??????
????}??????
?????
??????????
????public?void?doGet(HttpServletRequest?request,?HttpServletResponse?response)??????
????????????throws?ServletException,?IOException?{??????
??????????????
????}??????
?????
??????????
????public?void?doPost(HttpServletRequest?request,?HttpServletResponse?response)??????
????????????throws?ServletException,?IOException?{??????
????????doGet(request,?response);?????????????
????}??????
?????
????//?init方法启动定时器??????
????public?void?init()?throws?ServletException?{??????
??????????????
????????ServletContext?context?=?getServletContext();??????
??????????????
????????//?(true为用定时间刷新缓存)??????
????????String?startTask?=?getInitParameter("startTask");??????
??????????????????????
????????//?定时刷新时间(分钟)??????
????????Long?delay?=?Long.parseLong(getInitParameter("delay"));??????
??????????????
????????//?启动定时器??????
????????if(startTask.equals("true")){??????
????????????timer1?=?new?Timer(true);??????
????????????task1?=?new?Task(context);??????
????????????timer1.schedule(task1,?delay?*?60?*?1000,?delay?*?60?*?1000);??????
????????}??????
????}??????
}??????

定时执行操作?

?????

Java代码?

/**????
?*?????
?*?@author?callan????
?*/?????
import?java.util.TimerTask;??????
?????
import?javax.servlet.ServletContext;??????
?????
public?class?Task?extends?TimerTask{??????
?????
????private?ServletContext?context;??????
??????????
????private?static?boolean?isRunning?=?true;??????
??????????
????public?Task(ServletContext?context){??????
????????this.context?=?context;??????
????}??????
??????????
??????????????
????@Override?????
????public?void?run()?{??????
????????if(isRunning){??????
????????????????
????????}??????
????}??????
?????
}??????

在web.xml配置这个servlet为服务启动时就调用servlet?

< servlet >?
???? < servlet-name >taskservlet< / servlet-name >?
??? < servlet-class >com.task< /servlet-class >?
??? < init-param >?
???? < param-name >startTask< /param-name >?
???? < param-value >true< /param-value >?
??? < /init-param >?
??? < init-param >?
???? < param-name >intervalTime< /param-name >?
???? < param-value >1< /param-value >?
??? < /init-param >?
??? < load-on-startup >300< /load-on-startup >?
? < /servlet >?