【Spring】Spring的定时任务

> 参考的优秀文章

Task Execution and Scheduling

> 版本说明

<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>3.2.14.RELEASE</version>
</dependency>

<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-webflow</artifactId>
<version>2.3.4.RELEASE</version>
</dependency>

<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.1.0</version>
</dependency>
</dependencies>

> 搭建最简单的Spring定时任务工程

Spring定时任务，给人的第一感觉就是简洁(>_<)

所需要的JAR，参考以上“版本说明”的POM文件，当然，不嫌麻烦，也可以一个个去下载。

把Spring通过web.xml注册进来

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath*:spring/spring.xml</param-value>
</context-param>

<listener>
<description>Spring Context</description>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

当然，需要告诉Spring去哪儿扫描组件。对了，也要告诉Spring我们是使用注解方式注册任务的

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:util="http://www.springframework.org/schema/util"
xmlns:mvc="http://www.springframework.org/schema/mvc"
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/context http://www.springframework.org/schema/context/spring-context-3.2.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-3.2.xsd"> 
<context:component-scan base-package="com.nicchagil.*"/>
<task:annotation-driven/>

</beans>

附logback的配置

<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<!-- encoders are assigned the type ch.qos.logback.classic.encoder.PatternLayoutEncoder
by default -->
<encoder>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
</pattern>
</encoder>
</appender>

<appender name="FILE" class="ch.qos.logback.core.FileAppender">
<file>D:/logs/application.log</file>
<encoder>
<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
</pattern>
</encoder>
</appender>

<root level="debug">
<appender-ref ref="STDOUT" />
<appender-ref ref="FILE" />
</root>
</configuration>

好了，注册一个简单的任务，它每逢0秒执行，打印一个语句

package com.nicchagil.springtask;

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

@Component
public class MyFirstSpringJob {

private final Logger logger = LoggerFactory.getLogger(this.getClass());

@Scheduled(cron = "0 * * * * ?")
public void run() {
logger.info("MyFirstSpringJob trigger...");
}

}

如无意外，启动项目后，可见日志大致如下

22:42:00.024 [pool-1-thread-1] INFO  c.n.springtask.MyFirstSpringJob - MyFirstSpringJob trigger...
22:43:00.002 [pool-1-thread-1] INFO  c.n.springtask.MyFirstSpringJob - MyFirstSpringJob trigger...

> 如果你同时执行多个任务，且某些任务耗时较长，要配线程池哦(>_<)

如题。比如，你设置了12:00触发A任务、12:05触发B任务，如果A任务需耗时10分钟，并且没设置线程池，那么B任务有可能会被推迟到12:10以后再执行哦。

所以，这些情况，我们需设置线程池

<task:annotation-driven scheduler="myScheduler"/>
<task:scheduler id="myScheduler" pool-size="20"/>

注：具体池的大小，视项目情况而定

将任务改为如下测试

第一个任务

package com.nicchagil.springtask;

import java.util.concurrent.TimeUnit;

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

@Component
public class MyFirstSpringJob {

private final Logger logger = LoggerFactory.getLogger(this.getClass());

@Scheduled(cron = "0 * * * * ?")
public void run() {
logger.info("MyFirstSpringJob trigger...");

/* 模拟此Job需耗时5秒 */
try {
TimeUnit.SECONDS.sleep(5);
} catch (InterruptedException e) {
e.printStackTrace();
}
}

}

第二个任务

package com.nicchagil.springtask;

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

@Component
public class MySecondSpringJob {

private final Logger logger = LoggerFactory.getLogger(this.getClass());

@Scheduled(cron = "3 * * * * ?")
public void run() {
logger.info("MySecondSpringJob trigger...");
}

}

由日志可以看出，第一个任务由一个线程执行；而第二个任务启动时，由于第一个任务还未完成，则由另外一个线程执行

22:49:00.023 [myScheduler-1] INFO  c.n.springtask.MyFirstSpringJob - MyFirstSpringJob trigger...
22:49:03.002 [myScheduler-2] INFO  c.n.springtask.MySecondSpringJob - MySecondSpringJob trigger...