import java.util.Timer;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyListener implements ServletContextListener {
 
  private Timer timer = null;

  public void contextInitialized(ServletContextEvent event) {
    timer = new Timer(true);
    //设置任务计划，启动和间隔时间
    timer.schedule(new MyTask(), 0, 86400000);
  }

  public void contextDestroyed(ServletContextEvent event) {
    timer.cancel();
  }
 
}
MyTask：
import java.util.TimerTask;

public class MyTask extends TimerTask {

  public void run() {
    // System.out.println("call at " + (new Date()));
    // TODO 此处添加具体任务代码
  }

}
web.xml配置：
<listener>
<listener-class>com.fastunit.samples.listener.MyListener</listener-class>
</listener>