Spring是一个轻量级的控制反转(IoC)和面向切面(AOP)的容器框架，可以用它来实现很多的功能，其中比较简单就是定时器。下面我们基于xml配置来实现Spring定时任务。

定时任务组件分为三个：调度器、任务以及执行时间点。我们需要引入bean、context、core三个spring包。

application.xml

<?xml version="1.0" encoding="UTF-8"?>    
<beans xmlns="http://www.springframework.org/schema/beans"    
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:p="http://www.springframework.org/schema/p"  
    xmlns:aop="http://www.springframework.org/schema/aop"   
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:jee="http://www.springframework.org/schema/jee"  
    xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="    
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd  
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd  
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd  
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-4.0.xsd  
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
        http://www.springframework.org/schema/task 
        http://www.springframework.org/schema/task/spring-task-3.0.xsd">  
	<!-- 创建一个调度器 -->
	<task:scheduler id="schedualer"/>
	<!-- 配置任务类的bean -->
	<bean id="xmlTask" class="wokao666.club.spring_task.tasks.XmlTask"></bean>
	<task:scheduled-tasks scheduler="schedualer">
		<!-- 每2秒执行一次 -->
		<task:scheduled ref="xmlTask" method="say" cron="0/2 * * * * ?"/>
	</task:scheduled-tasks>
</beans>

XmlTask.java

package wokao666.club.spring_task.tasks;

import java.text.SimpleDateFormat;

import wokao666.club.spring_task.util.DateFormatter;

/**
 * 基于XML的spring定时任务
 */
public class XmlTask {
    public void say() {
        SimpleDateFormat format = DateFormatter.getDateFormatter();
        System.err.println(format.format(System.currentTimeMillis()) + " I am spring xml-based task!");
    }
}

DateFormatter.java

package wokao666.club.spring_task.util;

import java.text.SimpleDateFormat;

/**
 * 日期格式
 * @author hjw
 *
 */
public class DateFormatter {
    private static volatile SimpleDateFormat formater = null;
    private DateFormatter() {}
    public static SimpleDateFormat getDateFormatter() {
        if(null == formater) {
            synchronized (DateFormatter.class) {
                if(null == formater) {
                    formater = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
                }
            }
        }
    return formater;
    }
}

App.java

package wokao666.club.spring_task;

import org.springframework.context.support.ClassPathXmlApplicationContext;


/**
 * Hello world!
 *
 */
public class App 
{
    private static ClassPathXmlApplicationContext ctx;
    public static void main( String[] args ) {
            ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
    }
}

程序输出：

六月 10, 2018 10:47:11 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2328c243: startup date [Sun Jun 10 22:47:11 CST 2018]; root of context hierarchy
六月 10, 2018 10:47:11 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
信息: Loading XML bean definitions from class path resource [applicationContext.xml]
六月 10, 2018 10:47:12 下午 org.springframework.scheduling.concurrent.ExecutorConfigurationSupport initialize
信息: Initializing ExecutorService  'schedualer'
2018-06-10 10:47:14 I am spring xml-based task!
2018-06-10 10:47:16 I am spring xml-based task!
2018-06-10 10:47:18 I am spring xml-based task!

好了，上面就是基于xml配置实现Spring定时任务。对其中的代码有不理解的小伙伴，可以到动力节点在线的Spring视频教程查看对应的课程，有老师作出详细的讲解哦。