Cron 表達(dá)式是表示時(shí)間周期的字符串，常用于各種定時(shí)任務(wù)解決方案蠕蚜，本文中代碼示例基于 Spring @Scheduled 定時(shí)器
語(yǔ)法格式
Cron 字符串包含 6 或 7 個(gè)域麸塞，域之間使用空格分隔。
包含 6 個(gè)域的 Cron 表達(dá)式語(yǔ)法格式：
Seconds Minutes Hours DayofMonth Month DayofWeek
包含 7 個(gè)域的 Cron 表達(dá)式語(yǔ)法格式：
Seconds Minutes Hours DayofMonth Month DayofWeek Year
有效字符范圍
每個(gè)域可使用的有效字符包括：
Seconds：0~59 的整數(shù)，或
,-*/四個(gè)字符
Minutes：同 Seconds 域一致
Hours：0~23的整數(shù)兴垦，或,-*/四個(gè)字符
DayofMonth：0~31的整數(shù)，或,-*/?LWC八個(gè)字符
Month：1~12的整數(shù)字柠，或 JAN ~ DEC探越，或,-*/四個(gè)字符
DayofWeek：1~7的整數(shù)，或 SUN ~ SAT窑业，或,-*/?LC#八個(gè)字符钦幔，注意整數(shù) 1 代表星期日，每周第一天從周日開(kāi)始
Year：1970~2099常柄，或,-*/四個(gè)字符
特殊字符說(shuō)明
(1) ,
用于分隔枚舉值鲤氢，如在 Seconds 域使用 10,15,25 表示在第 10 秒、15 秒和 25 秒觸發(fā)一次西潘，示例代碼如下：
@Scheduled(cron = "10,15,25 * * * * ?")
public void scheduledTask() {
System.out.println("Task executed at " + LocalDateTime.now());
}
運(yùn)行日志：
2018-08-01 22:42:53.322 INFO 18140 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Starting DemoSpringBootScheduledApplication on LAPTOP-C375ASPB with PID 18140 (D:\JYL\DEV\IdeaProjects\demo\demo-spring-boot-scheduled\target\classes started by Ji in D:\JYL\DEV\IdeaProjects\demo)
2018-08-01 22:42:53.326 INFO 18140 --- [ main] s.b.s.DemoSpringBootScheduledApplication : No active profile set, falling back to default profiles: default
2018-08-01 22:42:53.382 INFO 18140 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@77e4c80f: startup date [Wed Aug 01 22:42:53 CST 2018]; root of context hierarchy
2018-08-01 22:42:54.517 INFO 18140 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-08-01 22:42:54.538 INFO 18140 --- [ main] s.a.ScheduledAnnotationBeanPostProcessor : No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-08-01 22:42:54.563 INFO 18140 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Started DemoSpringBootScheduledApplication in 1.521 seconds (JVM running for 1.976)
Task executed at 2018-08-01T22:43:10.007
Task executed at 2018-08-01T22:43:15.001
Task executed at 2018-08-01T22:43:25.001
Task executed at 2018-08-01T22:44:10.001
Task executed at 2018-08-01T22:44:15.001
Task executed at 2018-08-01T22:44:25.001
Task executed at 2018-08-01T22:45:10.001
Task executed at 2018-08-01T22:45:15.001
Task executed at 2018-08-01T22:45:25.001
......
(2) -
用于表示范圍卷玉，如在 Seconds 域使用 30-45 表示在第 30 秒至 45 秒范圍內(nèi)，每秒觸發(fā)一次喷市，示例代碼如下：
@Scheduled(cron = "30-45 * * * * ?")
public void scheduledTask() {
System.out.println("Task executed at " + LocalDateTime.now());
}
運(yùn)行日志：
2018-08-01 22:46:51.549 INFO 11236 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Starting DemoSpringBootScheduledApplication on LAPTOP-C375ASPB with PID 11236 (D:\JYL\DEV\IdeaProjects\demo\demo-spring-boot-scheduled\target\classes started by Ji in D:\JYL\DEV\IdeaProjects\demo)
2018-08-01 22:46:51.552 INFO 11236 --- [ main] s.b.s.DemoSpringBootScheduledApplication : No active profile set, falling back to default profiles: default
2018-08-01 22:46:51.600 INFO 11236 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@b7f23d9: startup date [Wed Aug 01 22:46:51 CST 2018]; root of context hierarchy
2018-08-01 22:46:52.524 INFO 11236 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-08-01 22:46:52.544 INFO 11236 --- [ main] s.a.ScheduledAnnotationBeanPostProcessor : No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-08-01 22:46:52.566 INFO 11236 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Started DemoSpringBootScheduledApplication in 1.29 seconds (JVM running for 1.72)
Task executed at 2018-08-01T22:47:30.007
Task executed at 2018-08-01T22:47:31.002
Task executed at 2018-08-01T22:47:32.001
Task executed at 2018-08-01T22:47:33.001
Task executed at 2018-08-01T22:47:34.001
Task executed at 2018-08-01T22:47:35.001
Task executed at 2018-08-01T22:47:36.001
Task executed at 2018-08-01T22:47:37.001
Task executed at 2018-08-01T22:47:38.002
Task executed at 2018-08-01T22:47:39.001
Task executed at 2018-08-01T22:47:40.001
Task executed at 2018-08-01T22:47:41
Task executed at 2018-08-01T22:47:42.002
Task executed at 2018-08-01T22:47:43.002
Task executed at 2018-08-01T22:47:44.001
Task executed at 2018-08-01T22:47:45.002
Task executed at 2018-08-01T22:48:30.001
Task executed at 2018-08-01T22:48:31
Task executed at 2018-08-01T22:48:32.002
Task executed at 2018-08-01T22:48:33.001
Task executed at 2018-08-01T22:48:34.001
Task executed at 2018-08-01T22:48:35.001
Task executed at 2018-08-01T22:48:36.001
Task executed at 2018-08-01T22:48:37.001
Task executed at 2018-08-01T22:48:38.002
Task executed at 2018-08-01T22:48:39.001
Task executed at 2018-08-01T22:48:40.001
Task executed at 2018-08-01T22:48:41.001
Task executed at 2018-08-01T22:48:42.001
Task executed at 2018-08-01T22:48:43.002
Task executed at 2018-08-01T22:48:44
Task executed at 2018-08-01T22:48:45.001
......
(3) *
匹配所在域有效范圍內(nèi)的任意值相种，如在 Minutes 域使用則每分鐘觸發(fā)一次，示例代碼如下：
@Scheduled(cron = "0 * * * * ?")
public void scheduledTask() {
System.out.println("Task executed at " + LocalDateTime.now());
}
運(yùn)行日志：
2018-08-01 22:50:18.396 INFO 12632 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Starting DemoSpringBootScheduledApplication on LAPTOP-C375ASPB with PID 12632 (D:\JYL\DEV\IdeaProjects\demo\demo-spring-boot-scheduled\target\classes started by Ji in D:\JYL\DEV\IdeaProjects\demo)
2018-08-01 22:50:18.402 INFO 12632 --- [ main] s.b.s.DemoSpringBootScheduledApplication : No active profile set, falling back to default profiles: default
2018-08-01 22:50:18.491 INFO 12632 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@709ba3fb: startup date [Wed Aug 01 22:50:18 CST 2018]; root of context hierarchy
2018-08-01 22:50:20.218 INFO 12632 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-08-01 22:50:20.260 INFO 12632 --- [ main] s.a.ScheduledAnnotationBeanPostProcessor : No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-08-01 22:50:20.288 INFO 12632 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Started DemoSpringBootScheduledApplication in 2.406 seconds (JVM running for 3.198)
Task executed at 2018-08-01T22:51:00.007
Task executed at 2018-08-01T22:52:00.001
Task executed at 2018-08-01T22:53:00.001
......
(4) /
表示從起始時(shí)間開(kāi)始品姓，每隔固定時(shí)間觸發(fā)一次寝并，如在 Seconds 域使用 10/15 表示每分鐘內(nèi)第 10 秒觸發(fā)以后，后續(xù)每隔 15 秒觸發(fā)一次腹备，即每分鐘第 10 秒食茎、第 25 秒、第 40 秒和第 55 秒各觸發(fā)一次馏谨。注意：這種間隔循環(huán)只在每分鐘內(nèi)執(zhí)行别渔，即第 55 秒時(shí)中斷每 15 秒的間隔循環(huán)，等到下一分鐘的第 10 秒再次執(zhí)行。
@Scheduled(cron = "10/15 * * * * ?")
public void scheduledTask() {
System.out.println("Task executed at " + LocalDateTime.now());
}
運(yùn)行日志：
2018-08-01 22:56:12.082 INFO 14064 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Starting DemoSpringBootScheduledApplication on LAPTOP-C375ASPB with PID 14064 (D:\JYL\DEV\IdeaProjects\demo\demo-spring-boot-scheduled\target\classes started by Ji in D:\JYL\DEV\IdeaProjects\demo)
2018-08-01 22:56:12.085 INFO 14064 --- [ main] s.b.s.DemoSpringBootScheduledApplication : No active profile set, falling back to default profiles: default
2018-08-01 22:56:12.131 INFO 14064 --- [ main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@1dd92fe2: startup date [Wed Aug 01 22:56:12 CST 2018]; root of context hierarchy
2018-08-01 22:56:12.962 INFO 14064 --- [ main] o.s.j.e.a.AnnotationMBeanExporter : Registering beans for JMX exposure on startup
2018-08-01 22:56:12.976 INFO 14064 --- [ main] s.a.ScheduledAnnotationBeanPostProcessor : No TaskScheduler/ScheduledExecutorService bean found for scheduled processing
2018-08-01 22:56:12.988 INFO 14064 --- [ main] s.b.s.DemoSpringBootScheduledApplication : Started DemoSpringBootScheduledApplication in 1.191 seconds (JVM running for 1.68)
Task executed at 2018-08-01T22:56:25.005
Task executed at 2018-08-01T22:56:40.001
Task executed at 2018-08-01T22:56:55.001
Task executed at 2018-08-01T22:57:10.001
Task executed at 2018-08-01T22:57:25.002
Task executed at 2018-08-01T22:57:40.002
Task executed at 2018-08-01T22:57:55
Task executed at 2018-08-01T22:58:10.002
......
(5) ?
只能用于 DayofMonth 和 DayofWeek 這兩個(gè)域哎媚，表示匹配任意值喇伯，如 DayofMonth 域使用固定值 10（表示每月第 10 天觸發(fā)），則 DayofWeek 使用 ?拨与，示例代碼如下：
@Scheduled(cron = "* * * 10 * ?")
public void scheduledTask() {
System.out.println("Task executed at " + LocalDateTime.now());
}
