Detailed cron expression
A Cron expression is a string. The string is separated by 5 or 6 spaces and divided into 6 or 7 fields. Each field represents a meaning. Cron has the following two syntax formats:
Seconds Minutes Hours DayofMonth Month DayofWeek Year或
Seconds Minutes Hours DayofMonth Month DayofWeek
The characters that can appear in each field are as follows:
Seconds: Four characters of ", - * /" can appear, and the valid range is an integer from 0-59.
Minutes: Four characters of ", - * /" can appear, and the valid range is 0- 59 integer
Hours: can appear ", - * /" four characters, the valid range is 0-23 integer
DayofMonth: can appear ", - * / ? LW C" eight characters, the valid range is 0-31 integer
Month: four characters ", - * /" can appear, and the valid range is an integer of 1-12 or JAN-DEc
DayofWeek: ", - * / ? LC #" can appear four characters, and the valid range is 1-7. Integer or SUN-SAT two ranges. 1 means Sunday, 2 means Monday, and so on
Year: four characters ", - * /" can appear, and the valid range is 1970-2099
Each field uses numbers, but the following special characters can also appear, and their meanings are:
(1)*: Indicates any value that matches the field. If you use * in the Minutes field, it means that an event will be triggered every minute.
(2)?: It can only be used in the fields of DayofMonth and DayofWeek. It also matches arbitrary values of the domain, but doesn't actually. Because DayofMonth and DayofWeek will affect each other. For example, if you want to trigger the scheduling on the 20th of each month, no matter what day of the week the 20th is, you can only use the following notation: 13 13 15 20 * ?, where the last digit can only be used? , and cannot use *, if you use * to indicate that it will trigger regardless of the day of the week, which is not the case.
(3)-: Indicates the range, for example, 5-20 is used in the Minutes field, indicating that it is triggered every minute from 5 minutes to 20 minutes
(4)/: Indicates that the start time starts to trigger, and then triggers every fixed time, for example, in The Minutes field uses 5/20, which means that it is triggered once in 5 minutes, and 25, 45, etc. are triggered once.
(5),: Indicates that the enumeration value is listed. For example: use 5,20 in the Minutes field, it means to fire every minute at 5 and 20 minutes.
(6) L: Indicates the last, which can only appear in the DayofWeek and DayofMonth fields. If 5L is used in the DayofWeek field, it means that it is triggered on the last Thursday.
(7) W: Indicates a valid working day (Monday to Friday), which can only appear in the DayofMonth field, and the system will trigger the event on the valid working day closest to the specified date. For example: use 5W on DayofMonth, if the 5th is Saturday, it will trigger on the nearest weekday: Friday, which is the 4th. If the 5th is Sunday, it will trigger on the 6th (Monday); if the 5th is one of Monday to Friday, it will trigger on the 5th. Another point, W's most recent search will not span the month
(8) LW: these two characters can be used together to indicate the last working day in a certain month, that is, the last Friday.
(9)#: Used to determine the day of the week in each month, which can only appear in the DayofMonth field. For example, in 4#2, it means the second Wednesday of a month.
举几个例子:
0 0 2 1 * ? * 表示在每月的1日的凌晨2点调度任务
0 15 10 ? * MON-FRI 表示周一到周五每天上午10：15执行作业
0 15 10 ? 6L 2002-2006 表示2002-2006年的每个月的最后一个星期五上午10:15执行作
一个cron表达式有至少6个（也可能7个）有空格分隔的时间元素。
按顺序依次为
秒（0~59）
分钟（0~59）
小时（0~23）
天（月）（0~31，但是你需要考虑你月的天数）
月（0~11）
天（星期）（1~7 1=SUN 或 SUN，MON，TUE，WED，THU，FRI，SAT）
年份（1970－2099）
其中每个元素可以是一个值(如6),一个连续区间(9-12),一个间隔时间(8-18/4)(/表示每隔4小时),一个列表(1,3,5),通配符。由于"月份中的日期"和"星期中的日期"这两个元素互斥的,必须要对其中一个设置?
0 0 10,14,16 * * ? 每天上午10点，下午2点，4点
0 0/30 9-17 * * ? 朝九晚五工作时间内每半小时
0 0 12 ? * WED 表示每个星期三中午12点
"0 0 12 * * ?" 每天中午12点触发
"0 15 10 ? * *" 每天上午10:15触发
"0 15 10 * * ?" 每天上午10:15触发
"0 15 10 * * ? *" 每天上午10:15触发
"0 15 10 * * ? 2005" 2005年的每天上午10:15触发
"0 * 14 * * ?" 在每天下午2点到下午2:59期间的每1分钟触发
"0 0/5 14 * * ?" 在每天下午2点到下午2:55期间的每5分钟触发
"0 0/5 14,18 * * ?" 在每天下午2点到2:55期间和下午6点到6:55期间的每5分钟触发
"0 0-5 14 * * ?" 在每天下午2点到下午2:05期间的每1分钟触发
"0 10,44 14 ? 3 WED" 每年三月的星期三的下午2:10和2:44触发
"0 15 10 ? * MON-FRI" 周一至周五的上午10:15触发
"0 15 10 15 * ?" 每月15日上午10:15触发
"0 15 10 L * ?" 每月最后一日的上午10:15触发
"0 15 10 ? * 6L" 每月的最后一个星期五上午10:15触发
"0 15 10 ? * 6L 2002-2005" 2002年至2005年的每月的最后一个星期五上午10:15触发
"0 15 10 ? * 6#3" 每月的第三个星期五上午10:15触发
有些子表达式能包含一些范围或列表
例如：子表达式（天（星期））可以为 “MON-FRI”，“MON，WED，FRI”，“MON-WED,SAT”
“*”字符代表所有可能的值
因此，“*”在子表达式（月）里表示每个月的含义，“*”在子表达式（天（星期））表示星期的每一天
“/”字符用来指定数值的增量
例如：在子表达式（分钟）里的“0/15”表示从第0分钟开始，每15分钟
在子表达式（分钟）里的“3/20”表示从第3分钟开始，每20分钟（它和“3，23，43”）的含义一样
“？”字符仅被用于天（月）和天（星期）两个子表达式，表示不指定值
当2个子表达式其中之一被指定了值以后，为了避免冲突，需要将另一个子表达式的值设为“？”
“L” 字符仅被用于天（月）和天（星期）两个子表达式，它是单词“last”的缩写
但是它在两个子表达式里的含义是不同的。
在天（月）子表达式中，“L”表示一个月的最后一天
在天（星期）自表达式中，“L”表示一个星期的最后一天，也就是SAT
如果在“L”前有具体的内容，它就具有其他的含义了
例如：“6L”表示这个月的倒数第６天，“FRIL”表示这个月的最一个星期五
注意：在使用“L”参数时，不要指定列表或范围，因为这会导致问题
字段 允许值 允许的特殊字符
秒 0-59 , - * /
分 0-59 , - * /
小时 0-23 , - * /
日期 1-31 , - * ? / L W C
月份 1-12 或者 JAN-DEC , - * /
星期 1-7 或者 SUN-SAT , - * ? / L C #
年（可选） 留空, 1970-2099 , - * /