用Java自定义一个定时器

1.先定义一个监听类：

import java.util.Date;
import java.util.Timer;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class DemoListener implements ServletContextListener {

private Timer timer = new Timer();

public void contextDestroyed(ServletContextEvent event) {
        timer.cancel();
    }

public void contextInitialized(ServletContextEvent event) {
        Date firstTime = new Date(System.currentTimeMillis());
int period = 5;
// 设置定时的开始时间和周期
        timer.schedule(new DemoTask(), firstTime, period * 1000);
    }

}

2.制定定时任务类：

import java.net.UnknownHostException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.TimerTask;

import org.dom4j.DocumentException;

public class DemoTask extends TimerTask {
public void doSomething() throws UnknownHostException, DocumentException, ParseException {
// 调用动作


        System.out.println("定时调用动作成功--------------------------------------------------------------------");
    }

public void run() {
try {
            doSomething();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

3.web.xml配置监听类

<?xml version="1.0" encoding="ISO-8859-1"?>

<web-app>
<display-name>DemoTimer</display-name>
<listener>
<listener-class>DemoListener</listener-class>
</listener>
</web-app>