如何在Web程序中實現定時運行的功能？

定時器在Web中的應用

關鍵字: java定時器在web中的應用

在web中,定時器的啓動一般隨web server的啓動而啓動,一般有兩種方法. 

方法一：在web.xml裏配置一個Servlet，並設置其隨web server的啓動而啓動。然後在該Servlet的init()方法裏啓動定時器，在destory()方法裏銷燬定時器。 
方法二：在web.xml裏配置一個Listener,然後在該Listener的初始化方法裏啓動定時器，在其銷燬的方法朝左銷燬定時器。 

在servlet中啓動定時器 

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方法啓動定時器
    public void init() throws ServletException {

        ServletContext context = getServletContext();

        // (true爲用定時間刷新緩存)
        String startTask = getInitParameter("startTask");

        // 定時刷新時間(分鐘)
        Long delay = Long.parseLong(getInitParameter("delay"));

        // 啓動定時器
        if(startTask.equals("true")){
            timer1 = new Timer(true);
            task1 = new Task(context);
            timer1.schedule(task1, delay * 60 * 1000, delay * 60 * 1000);
        }
    }
}

定時執行操作 

     

/**
 *
 * @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配置這個servlet爲服務啓動時就調用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 >