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 

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 

     

/**
 *
 * @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 >