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 >