Spring 定时器的使用—Xml、Annotation、自定义

日常系统开发中定时任务用的非常地普遍，比如我们可能想做个定时器去查询某笔交易的状态并进行汇总，又或者我们想在凌晨4点清楚数据库的相关数据、又或者我们想在每月月底0点定时去开启一个事务对当月、季度的数据做统计做成报表，灰常多呀！我也说不完啦！

有一点小编对于定时任务的理解，那就是：定时任务只是告诉系统在某个时刻执行某个任务，而至于该任务什么时候执行完成，这不是定时任务要关心的范围，定时任务只需要保证某个时刻发出调用某个任务的指令即可。

在Java领域定时任务实现的佼佼者就是quartz了，quartz框架在spring 3.0之前用的很广泛，当然现在也是，quartz支持数据持久化以及相应的集群方式部署，spring 3.0 之后的spring版本自己实现了一套定时任务框架，我们可以把看做是quartz的低配版本，它没有提供对集群的支持，不过其他功能已经灰常强大啦！

跟随spring传统，spring自己实现的定时任务框架spring-task同时支持xml和注解方式配置定时任务，当然小编还会讲解我们如何自定义定时任务。翻开spring源码包我们可以发现，其实spring除了自家的spring-task,同时还提供了quartz的集成，关于spring如何集成quartz，请阅读小编之前写的一篇文章简单说说Java 定时任务框架—Quartz

下面我将分别从xml、注解、自定义3个方面讲解如何使用spring-task.

一、基于xml配置实现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!

二、基于注解的spring-task

applicationContext.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">  
        <!-- 开启注解驱动 -->
	<task:annotation-driven/>
	<!-- bean 扫描 -->
	<context:component-scan base-package="wokao666.club.spring_task.tasks"></context:component-scan>
</beans>

AnnotationTask.java

package wokao666.club.spring_task.tasks;

import java.text.SimpleDateFormat;

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Service;

import wokao666.club.spring_task.util.DateFormatter;
/** * 测试基于注解的定时任务 * @author hjw */
@Service
public class AnnotationTask {
    @Scheduled(cron="0/2 * * * * ?")
    public void say() {
        SimpleDateFormat format = DateFormatter.getDateFormatter();
        System.err.println(format.format(System.currentTimeMillis()) + " good morning");
    }
}

App.java、DateFormatter.java和上面一样，程序输出如下：

六月 10, 2018 10:53:45 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2328c243: startup date [Sun Jun 10 22:53:45 CST 2018]; root of context hierarchy
六月 10, 2018 10:53:45 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 10:53:46 下午 org.springframework.beans.factory.support.DefaultListableBeanFactory registerBeanDefinition
信息: Overriding bean definition for bean 'org.springframework.context.annotation.internalScheduledAnnotationProcessor' with a different definition: replacing [Generic bean: class [org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor]; scope=; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null] with [Root bean: class [null]; scope=; abstract=false; lazyInit=false; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=org.springframework.scheduling.annotation.SchedulingConfiguration; factoryMethodName=scheduledAnnotationProcessor; initMethodName=null; destroyMethodName=(inferred); defined in class path resource [org/springframework/scheduling/annotation/SchedulingConfiguration.class]]
六月 10, 2018 10:53:46 下午 org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor finishRegistration
信息: No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-06-10 10:53:48 good morning
2018-06-10 10:53:50 good morning
2018-06-10 10:53:52 good morning
2018-06-10 10:53:54 good morning

注意到上面输出No TaskScheduler/ScheduledExecutorService bean found for scheduled processing这句话，因为你可以传入一个java.util.Executor线程池对象来实现对异步任务的调用，如果你指定了executor属性，则spring会默认创建一个SimpleAsyncTaskExecutor对象去执行,executor属性指定定时任务执行的线程池，强调执行，而scheduler属性表示任务调度的线程池，因为spring默认是单线程串行调度，如果想允许多线程并发调度，则需要配置scheduler属性，配置示例如下：

<!-- 调度线程池 -->
<task:scheduler id="scheduler" pool-size="10" />
<!-- 任务执行线程池 -->
<task:executor id="executor" pool-size="10" />
<task:annotation-driven executor="executor" scheduler="scheduler"/>
<context:component-scan base-package="wokao666.club.spring_task.tasks"></context:component-scan>

(此处还需另行深入学习spring异步任务相关知识原理，异步执行使用@Async标注方法)

三、自定义定时任务

实现自定义定时任务，或者说我们可以更改相关的cron表达式，这看起来是很不可思议的，但确实可以做到，小编推荐一篇例文Spring @Scheduled定时任务动态修改cron参数

CustomSchedual.java

package wokao666.club.spring_task.tasks;

import org.springframework.scheduling.Trigger;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.SchedulingConfigurer;
import org.springframework.scheduling.config.ScheduledTaskRegistrar;
import org.springframework.scheduling.support.CronTrigger;
import org.springframework.stereotype.Component;

import wokao666.club.spring_task.util.DateFormatter;

/** * 演示自定义定时器 */
@EnableScheduling
@Component
public class CustomSchedual implements SchedulingConfigurer{
    
    private static String cron = "0/2 * * * * ?";
    
    private CustomSchedual() {
        new Thread(()->{
            try {
                Thread.sleep(16000);
            } catch (InterruptedException e) {}
            cron = "0/10 * * * * ?";
            System.err.println("change")
        }).start();
    }
    public void configureTasks(ScheduledTaskRegistrar arg0) {
        arg0.addTriggerTask(()->{
            System.err.println(DateFormatter.getDateFormatter().format(System.currentTimeMillis()) + " good night!");
        },(triggerContext)->{
        CronTrigger trigger = new CronTrigger(cron);
        return trigger.nextExecutionTime(triggerContext);
        });
    }
}

程序输出如下，可以看到，程序过来16秒之后，执行频率从2秒/次变为10秒/次：

六月 10, 2018 11:49:13 下午 org.springframework.context.support.AbstractApplicationContext prepareRefresh
信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2328c243: startup date [Sun Jun 10 23:49:13 CST 2018]; root of context hierarchy
六月 10, 2018 11:49:13 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 11:49:14 下午 org.springframework.scheduling.annotation.ScheduledAnnotationBeanPostProcessor finishRegistration
信息: No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-06-10 11:49:16 good night!
2018-06-10 11:49:18 good night!
2018-06-10 11:49:20 good night!
2018-06-10 11:49:22 good night!
2018-06-10 11:49:24 good night!
2018-06-10 11:49:26 good night!
2018-06-10 11:49:28 good night!
2018-06-10 11:49:30 good night!
change
2018-06-10 11:49:32 good night!
2018-06-10 11:49:40 good night!
2018-06-10 11:49:50 good night!
2018-06-10 11:50:00 good night!
2018-06-10 11:50:10 good night!
2018-06-10 11:50:20 good night!

最后，单纯会使用还不行，我们不仅要知其然，还要知其所以然，后期有时间多学学原理，其实底层无非就是java线程池的使用，加油，骚年们，晚安！