SpringTask定时任务的使用

　　实现定时任务简单的有四种方式:Timer\ScheduledThreadPool线程池\quartz(常用)，还有另一种就是springtask。

　　都说springtask上手简单，于是简单的研究一下springtask的使用，并且运用到自己的项目中。其也有两种配置方式，第一种是基于xml配置，第二种是基于注解。

　　SprngTask没有专门的包，其核心类位于spring-context包中。所以引入spring的核心包此功能即可使用。

　　在实际的项目中，我们经常将job作为action层，在job中注入service去操作底层的dao，或者定时的向其他系统拉取数据,再或者向其他系统推送数据。

1.基于xml配置的简单的使用

测试类:(每五秒钟打印一次日志)

package cn.xm.exam.job;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
@Component
public class FirstTestJob {
    private static final Logger log = LoggerFactory.getLogger(FirstTestJob.class);
    private static int count;

    public void cron() {
        log.info("spring task execute times {}", count++);
    }
}

xml配置:(非常类似于quartz的cron表达式和linux定时的cron表达式)

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd">

    <context:component-scan base-package="cn.xm.exam.job"></context:component-scan>

    <task:scheduled-tasks>
        <task:scheduled ref="firstTestJob" method="cron"
            cron="0/5 * * * * ?" />
    </task:scheduled-tasks>

</beans>

重点是引入task的schema:

xmlns:task="http://www.springframework.org/schema/task"
http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd

结果:

...
2018-11-14 22:35:00 [cn.xm.exam.job.FirstTestJob]-[INFO] spring task execute times 59
2018-11-14 22:35:05 [cn.xm.exam.job.FirstTestJob]-[INFO] spring task execute times 60
2018-11-14 22:35:10 [cn.xm.exam.job.FirstTestJob]-[INFO] spring task execute times 61
2018-11-14 22:35:15 [cn.xm.exam.job.FirstTestJob]-[INFO] spring task execute times 62
2018-11-14 22:35:20 [cn.xm.exam.job.FirstTestJob]-[INFO] spring task execute times 63
2018-11-14 22:35:25 [cn.xm.exam.job.FirstTestJob]-[INFO] spring task execute times 64
...

2.基于注解的使用

首先查看注解的源码:

注解使用必须在xml中开启注解任务，使注解生效:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.2.xsd">

    <context:component-scan base-package="cn.xm.exam.job"></context:component-scan>

    <!-- 开启注解任务 -->
    <task:annotation-driven />

</beans>

测试类:(每十秒钟打印一次日志)

package cn.xm.exam.job;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
public class FirstAnnotationJob {
    private static final Logger log = LoggerFactory.getLogger(FirstAnnotationJob.class);
    private static int count;

    @Scheduled(cron = "0/10 * * * * ?")
    public void cron() {
        log.info("spring anno task execute times {}", count++);
    }
}

结果:

2018-11-14 22:44:40 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 0
2018-11-14 22:44:50 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 1
2018-11-14 22:45:00 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 2
2018-11-14 22:45:10 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 3

查看@Scheduled的源码:(位于spring-context包内)

/** <a href="http://www.cpupk.com/decompiler">Eclipse Class Decompiler</a> plugin, Copyright (c) 2017 Chen Chao. */
package org.springframework.scheduling.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target({ElementType.METHOD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Scheduled {

    /**
     * A cron-like expression, extending the usual UN*X definition to include
     * triggers on the second as well as minute, hour, day of month, month
     * and day of week.  e.g. {@code "0 * * * * MON-FRI"} means once per minute on
     * weekdays (at the top of the minute - the 0th second).
     * @return an expression that can be parsed to a cron schedule
     * @see org.springframework.scheduling.support.CronSequenceGenerator
     */
    String cron() default "";

    /**
     * Execute the annotated method with a fixed period between the end
     * of the last invocation and the start of the next.
     * @return the delay in milliseconds
     */
    long fixedDelay() default -1;

    /**
     * Execute the annotated method with a fixed period between invocations.
     * @return the period in milliseconds
     */
    long fixedRate() default -1;

    /**
     * Number of milliseconds to delay before the first execution of a
     * {@link #fixedRate()} or {@link #fixedDelay()} task.
     * @return the initial delay in milliseconds
     * @since 3.2
     */
    long initialDelay() default 0;

}

参数解释:(其实源码的注释也写的非常清楚了)

cron:cron表达式

fixedDelay:表示从上一个任务完成开始到下一个任务开始的间隔，单位是毫秒

fixedRate:从上一个任务开始到下一个任务开始的间隔，单位是毫秒。

initialDelay:任务第一次被调用前的延时，单位毫秒。

需要注意的是上面的前三个属性只能保留一个，不能同时出现，最后一个延时操作可以与上面三个参数搭配。否则会报异常如下:

java.lang.IllegalArgumentException: Exactly one of the 'cron', 'fixedDelay', or 'fixedRate' attributes is required.

接下来我们测试上面的参数: 

fixedDelay :方法中模拟处理用了2s

package cn.xm.exam.job;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
public class FirstAnnotationJob {
    private static final Logger log = LoggerFactory.getLogger(FirstAnnotationJob.class);
    private static int count;

    @Scheduled(fixedDelay = 10000)
    public void cron() {
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            log.error("InterruptedException ", e);
        }
        log.info("spring anno task execute times {}", count++);
    }
}

结果:(实际每两次任务中间相差12s，也就是第一次任务结束10s后开启下次任务)

2018-11-14 23:02:04 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 1
2018-11-14 23:02:16 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 2
2018-11-14 23:02:28 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 3
2018-11-14 23:02:40 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 4

fixedRate测试:

package cn.xm.exam.job;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
public class FirstAnnotationJob {
    private static final Logger log = LoggerFactory.getLogger(FirstAnnotationJob.class);
    private static int count;

    @Scheduled(fixedRate = 10000)
    public void cron() {
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            log.error("InterruptedException ", e);
        }
        log.info("spring anno task execute times {}", count++);
    }
}

结果:(每两次任务相差10s，也就是本次任务开始之后10s后就开启下次任务，不管中间处理花费多长时间)

2018-11-14 23:04:47 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 1
2018-11-14 23:04:57 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 2
2018-11-14 23:05:07 [cn.xm.exam.job.FirstAnnotationJob]-[INFO] spring anno task execute times 3

至此完成了springtask的测试，确实比quartz简便的多，使用也简单。

附一个在线cron表达式生成器:http://cron.qqe2.com/