Cron 表达

Cron 表达式由六个连续字段组成 -

second, minute, hour, day of month, month, day(s) of week

并声明如下

@Scheduled(cron = "* * * * * *")

我们还可以将时区设置为 -

@Scheduled(cron="* * * * * *", zone="Europe/Istanbul")

备注： -

syntax            means                example                explanation*                 match any            "* * * * * *"          do always
*/x               every x              "*/5 * * * * *"        do every five seconds
?                 no specification     "0 0 0 25 12 ?"        do every Christmas Day

示例： -

syntax                        means"0 0 * * * *"                 the top of every hour of every day.
"*/10 * * * * *"              every ten seconds.
"0 0 8-10 * * *"              8, 9 and 10 o'clock of every day.
"0 0/30 8-10 * * *"           8:00, 8:30, 9:00, 9:30 and 10 o'clock every day.
"0 0 9-17 * * MON-FRI"        on the hour nine-to-five weekdays
"0 0 0 25 12 ?"               every Christmas Day at midnight

对于每个匹配的情况，都会显式调用使用 @Scheduled() 声明的方法。

如果我们想要在满足 cron 表达式时执行某些代码，那么我们必须在注释中指定它：

@Component
public class MyScheduler{    
    
    @Scheduled(cron="*/5 * * * * MON-FRI")
    public void doSomething() {
        // this will execute on weekdays
    }
}

如果我们想在 5 秒内每次在我们的控制台中打印当前时间 -

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

import java.text.SimpleDateFormat;
import java.util.Date;

@Component
public class Scheduler {

    private static final Logger log = LoggerFactory.getLogger(Scheduler.class);
    private static final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");

    @Scheduled(cron = "*/5 * * * * *")
    public void currentTime() {
        log.info("Current Time      = {}", dateFormat.format(new Date()));
    }

}

使用 XML 配置的示例：

示例类：

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import java.text.SimpleDateFormat;
import java.util.Date;

@Component("schedulerBean")
public class Scheduler {

    private static final Logger log = LoggerFactory.getLogger(Scheduler.class);
    private static final SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");

    public void currentTime() {
        log.info("Current Time      = {}", dateFormat.format(new Date()));
    }

}  

示例 XML（task-context.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:task="http://www.springframework.org/schema/task"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
        http://www.springframework.org/schema/task 
        http://www.springframework.org/schema/task/spring-task-4.1.xsd">

    <task:scheduled-tasks scheduler="scheduledTasks">
        <task:scheduled ref="schedulerBean" method="currentTime" cron="*/5 * * * * MON-FRI" />
    </task:scheduled-tasks>

    <task:scheduler id="scheduledTasks" />

</beans>