java的任务监听器监听任务

Java自带的java.util.Timer类，这个类允许你调度一个java.util.TimerTask任务。

使用这种方式可以让你的程序按照某一个频度执行，但不能在指定时间运行。一般用的较少

监听器类：

package com.tech.jin.listener;

import java.util.Timer;
import java.util.TimerTask;

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

import org.apache.log4j.Logger;
import org.springframework.web.context.support.WebApplicationContextUtils;

import com.tech.jin.task.OneTask;
import com.tech.jin.util.Const;

/**
 * 任务监听器 需要配置在web.xml的listener中
 * @author Administrator
 *
 */
public class TaskListener implements ServletContextListener{

    private Logger logger = Logger.getLogger(TaskListener.class);
    private ServletContext context = null;
    private Timer timer = null;

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        logger.info("TaskListener contextDestroyed...");
        timer.cancel();
        context = null;
    }

    @Override
    public void contextInitialized(ServletContextEvent event) {
        logger.info("TaskListener contextInitialized...");

        context = event.getServletContext();
        //如果使用spring框架，可将context放入到一个工具类中的常量，用来取到WebApplicationContext
//        Const.WEB_APP_CONTEXT = WebApplicationContextUtils.getWebApplicationContext(context);

        logger.info("定时器开始初始化...");
        timer = new Timer();

        logger.info("定时任务OneTask创建...");
        TimerTask task = new OneTask(context);
        long period = 60*60*1000;//每隔1小时
        timer.schedule(task, 0, period);
        logger.info("定时任务OneTask已添加到任务调度...");

        //TODO

    }

}

任务类：

package com.tech.jin.task;

import java.util.Calendar;
import java.util.TimerTask;

import javax.servlet.ServletContext;

import org.apache.log4j.Logger;

public class OneTask extends TimerTask{

    private Logger logger = Logger.getLogger(OneTask.class);
    private ServletContext context = null;
    private static final int taskExcuteTime = 15;//15点钟

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

    @Override
    public void run() {
        logger.info("OneTask run...");

        Calendar c = Calendar.getInstance();
        int currentHour = c.get(Calendar.HOUR_OF_DAY);//24小时制，取值0-24

        if(currentHour==taskExcuteTime){

            logger.info("任务开始...");

            try {

                doTask();//执行任务逻辑

            } catch (Exception e) {
                logger.error("任务执行异常："+e);
            }

            logger.info("任务结束...");

        }

    }

    public void doTask() throws InterruptedException{
        logger.info("doTask");

        logger.info("context:"+context);
    }

}

另一种是相比于Timer的单线程，它是通过线程池的方式来执行任务的。

package com.tech.jin.listener;

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

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

import org.apache.log4j.Logger;

import com.tech.jin.task.OneTask;

/**
 * 任务监听器 需要配置在web.xml的listener中
 * @author Administrator
 *
 */
public class TaskListener implements ServletContextListener{

    private Logger logger = Logger.getLogger(TaskListener.class);
    private ServletContext context = null;
    private Timer timer = null;

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        logger.info("TaskListener contextDestroyed...");
        timer.cancel();
        context = null;
    }

    @Override
    public void contextInitialized(ServletContextEvent event) {
        logger.info("TaskListener contextInitialized...");

        context = event.getServletContext();
        //如果使用spring框架，可将context放入到一个工具类中的常量，用来取到WebApplicationContext
//        Const.WEB_APP_CONTEXT = WebApplicationContextUtils.getWebApplicationContext(context);

        //1.定时任务实现方式一
/*        logger.info("定时器开始初始化...");
        timer = new Timer();

        logger.info("定时任务OneTask创建...");
        TimerTask task = new OneTask(context);
        long period = 60*60*1000;//每隔1小时
        timer.schedule(task, 0, period);
        logger.info("定时任务OneTask已添加到任务调度...");*/

        //2.定时任务实现方式二 相比于Timer的单线程，它是通过线程池的方式来执行任务的
        Runnable r = new Runnable() {

            @Override
            public void run() {
                // TODO Auto-generated method stub

            }
        };
        long initialDelay = 0;//创建对象马上执行
        long period = 1;//间隔一秒
        ScheduledExecutorService service = Executors.newSingleThreadScheduledExecutor();
        service.scheduleAtFixedRate(r, initialDelay, period, TimeUnit.SECONDS);

    }

}