Quartz wants a question mark
A medium Java puzzle in the scheduling and cron mistakes family. One line below contains a real bug. Try to spot it first, then read why it fails and how to fix it.
Highlighted: line 8. Play this one as a puzzle without the answer.
What is wrong
Quartz requires one of the day-of-month and day-of-week fields to be ? . Using * in both is rejected with a ParseException at schedule time. The name of the method also says weekdays, which this expression does not express.
The fix
How to avoid it next time
In Quartz put ? in the field you do not use, and prefer day names such as MON-FRI to numbers.
Want the background? Read Quartz scheduler in the Java concepts library.
About scheduling and cron mistakes
Cron dialects differ in field count and meaning. Spring has six fields starting with seconds, Unix has five, Quartz needs a question mark in one day field, and time zones decide when midnight actually is.
In code review: Count the fields and check which dialect the framework expects. Confirm the time zone and what the day-of-week field numbers mean in that dialect.
More puzzles in this family
Frequently asked questions
What is the bug in "Quartz wants a question mark"?
Quartz requires one of the day-of-month and day-of-week fields to be ? . Using * in both is rejected with a ParseException at schedule time. The name of the method also says weekdays, which this expression does not express. The faulty line is line 8: .withSchedule(CronScheduleBuilder.cronSchedule("0 0 9 * * *"))
How do I fix it?
Replace it with: CronScheduleBuilder.cronSchedule("0 0 9 ? * MON-FRI"). In Quartz put ? in the field you do not use, and prefer day names such as MON-FRI to numbers.
How do I catch scheduling and cron mistakes in code review?
Count the fields and check which dialect the framework expects. Confirm the time zone and what the day-of-week field numbers mean in that dialect.
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