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A web user interface for quartz
Documentation
Cron-Expressions are used to configure instances of CronTrigger.
Cron-Expressions are strings that are actually made up of seven
sub-expressions, that describe individual details of the schedule. These
sub-expression are separated with white-space, and represent:
1. Seconds
2. Minutes
3. Hours
4. Day-of-Month
5. Month
6. Day-of-Week
7. Year (optional field)
An example of a complete cron-expression is the string "0 0 12 ? * WED"
- which means "every Wednesday at 12:00 pm".
Individual sub-expressions can contain ranges and/or lists. For example,
the day of week field in the previous (which reads "WED") example could
be replaces with "MON-FRI", "MON, WED, FRI", or even "MON-WED,SAT".
Wild-cards (the '*' character) can be used to say "every" possible value
of this field. Therefore the '*' character in the "Month" field of the
previous example simply means "every month". A '*' in the Day-Of-Week
field would obviously mean "every day of the week".
All of the fields have a set of valid values that can be specified.
These values should be fairly obvious - such as the numbers 0 to 59 for
seconds and minutes, and the values 0 to 23 for hours. Day-of-Month can
be any value 0-31, but you need to be careful about how many days are in
a given month! Months can be specified as values between 0 and 11, or by
using the strings JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV
and DEC. Days-of-Week can be specified as vaules between 1 and 7 (1 =
Sunday) or by using the strings SUN, MON, TUE, WED, THU, FRI and SAT.
The '/' character can be used to specify increments to values. For
example, if you put '0/15' in the Minutes field, it means 'every 15
minutes, starting at minute zero'. If you used '3/20' in the Minutes
field, it would mean 'every 20 minutes during the hour, starting at
minute three' - or in other words it is the same as specifying '3,23,43'
in the Minutes field.
The '?' character is allowed for the day-of-month and day-of-week
fields. It is used to specify "no specific value". This is useful when
you need to specify something in one of the two fields, but not the
other. See the examples below (and CronTrigger JavaDoc) for
clarification.
The 'L' character is allowed for the day-of-month and day-of-week
fields. This character is short-hand for "last", but it has different
meaning in each of the two fields. For example, the value "L" in the
day-of-month field means "the last day of the month" - day 31 for
January, day 28 for February on non-leap years. If used in the
day-of-week field by itself, it simply means "7" or "SAT". But if used
in the day-of-week field after another value, it means "the last xxx day
of the month" - for example "6L" or "FRIL" both mean "the last friday of
the month". When using the 'L' option, it is important not to specify
lists, or ranges of values, as you'll get confusing results.
The 'W' is used to specify the weekday (Monday-Friday) nearest the given
day. As an example, if you were to specify "15W" as the value for the
day-of-month field, the meaning is: "the nearest weekday to the 15th of
the month".
The '#' is used to specify "the nth" XXX weekday of the month. For
example, the value of "6#3" or "FRI#3" in the day-of-week field means
"the third Friday of the month".
Here are a few more examples of expressions and their meanings - you can
find even more in the JavaDoc for CronTrigger
Example Cron Expressions
CronTrigger Example 1 - an expression to create a trigger that simply
fires every 5 minutes
"0 0/5 * * * ?"
CronTrigger Example 2 - an expression to create a trigger that fires
every 5 minutes, at 10 seconds after the minute (i.e. 10:00:10 am,
10:05:10 am, etc.).
"10 0/5 * * * ?"
CronTrigger Example 3 - an expression to create a trigger that fires at
10:30, 11:30, 12:30, and 13:30, on every Wednesday and Friday.
"0 30 10-13 ? * WED,FRI"
CronTrigger Example 4 - an expression to create a trigger that fires
every half hour between the hours of 8 am and 10 am on the 5th and 20th
of every month. Note that the trigger will NOT fire at 10:00 am, just at
8:00, 8:30, 9:00 and 9:30
"0 0/30 8-9 5,20 * ?"
Note that some scheduling requirements are too complicated to express
with a single trigger - such as "every 5 minutes between 9:00 am and
10:00 am, and every 20 minutes between 1:00 pm and 10:00 pm". The
solution in this scenario is to simply create two triggers, and register
both of them to run the same job.