Java定时器

1:

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class DingShi implements ServletContextListener
{
	private java.util.Timer timer = null;

	public void contextInitialized(ServletContextEvent event)
	{
		timer = new java.util.Timer(true);
		event.getServletContext().log("定时器已启动");
		System.out.println("启动");
		//每小时刷新
		timer.schedule(new MyTask(event.getServletContext()), 0,60*60*1000);		
                  event.getServletContext().log("已经添加任务调度表");
	}

	public void contextDestroyed(ServletContextEvent event)
	{
		timer.cancel();
		event.getServletContext().log("定时器销毁");
	}

}

2:

import java.util.TimerTask;
import javax.servlet.ServletContext;
public class MyTask extends TimerTask
{
	private static boolean isRunning = false;

	private ServletContext context = null;

	public MyTask(ServletContext context)
	{
		this.context = context;
	}

	public void run()
	{
		if (!isRunning)
		{
				isRunning = true;
				context.log("开始执行指定任务");
				//你要定时执行的方法
				//NewsDaoImp nd = new NewsDaoImp();
				//nd.dingshiTest();
				isRunning = false;
				context.log("指定任务执行结束");
		} 
		else
		{
			context.log("上一次任务执行还未结束");
		}
	}

}

3：web.xml配置文件中添加
<listener>
<listener-class>cn.com.sns.www.view.DingShi</listener-class>
</listener>