这个 CRON 表达式的间隔是多少？

Question

I am unable to decode the interval defined in the CRON expression below, Please explain it with some details.

@Scheduled(cron = "0 0/1 * 1/1 * ?")

I understand the basic structure of a CRON sequence but I can't find what does 0/1 or 1/1 means?

Answer 1

In a cron expression, the various fields have a strict range which values are allowed:

field          allowed values
-----          --------------
minute         0-59
hour           0-23
day of month   1-31
month          1-12 (or names, see below)
day of week    0-7 (0 or 7 is Sunday, or use names)

A field may contain an <asterisk> ( * ), which always stands for <first>-<last> . Another possibility is ranges of numbers . Ranges are two numbers separated with a <hyphen> ( - ). The specified range is inclusive. For example, 8-11 matches all number 8,9,10,11

In combination with ranges, you can have a step value , noted as /<number> which tells you how many numbers should be skipped in the range. Example: 2-7/2 allows the numbers 2,4,6 .

In some cron-systems, the notation <start>/<number> is a shorthand for <start>-<last>/<number> . Such an example is the Quartz Job Scheduling Library:

The / character can be used to specify increments to values. For example, if you put 0/15 in the Minutes field, it means every 15th minute of the hour, starting at minute zero . If you used 3/20 in the Minutes field, it would mean every 20th minute of the hour, starting at minute three – or in other words it is the same as specifying 3,23,43 in the Minutes field. Note the subtlety that /35 does *not mean every 35 minutes - it means every 35th minute of the hour, starting at minute zero – or in other words the same as specifying 0,35 .

_{source: Quartz Job Scheduling Library Manual}