Time-based Job Scheduling Section¶
In the Triggers section tab the moments in which the job will be executed are configured. It is possible to add various time-based scheduling configurations for each job, each one of which will have an associated expression in the cron format (see section Syntax for the Cron Expression).
Optionally, you can assign a start and end time (Start time and End time respectively) for the job. In that case, the job will only be executed when specified by the cron expression and when, in addition, the current time is in the specified interval. The start and end times can be entered manually, respecting the syntax yyyy-MM-dd and HH:mm for date and time, respectively or by using the calendars associated with each field.
Also optionally, it is possible to define dependencies of the trigger with other jobs, so that the execution of this trigger will wait until the dependent jobs have successfully finished (see section Dependencies Among Jobs for more information).
By default, the cron expression generated represents the execution of the job every day at midnight. The cron expression can be entered manually (see syntax in section Syntax for the Cron Expression) or visually using the visual editor for cron expressions.
The visual editor allows specifying the minutes/hours/days/months and days of the week in which the job will run (the value for seconds is not visually configurable, assumed equal to 0). It is also possible to specify typical periodical schedules such as “every day” or “every five minutes, every day”.
By manually writing the cron expression, it is possible to specify configurations that cannot visually configured (see section Syntax for the Cron Expression)
Syntax for the Cron Expression¶
Quartz cron expressions are used. The expressions are comprised of 6 required fields and one optional field separated by white space. The job will be executed when the expression has values in all the fields that coincide with the current time. The fields respectively are described as follows:
|Field Name||Allowed Values||Allowed Special Characters|
|Seconds||0-59||, - * /|
|Minutes||0-59||, - * /|
|Hours||0-23||, - * /|
|Day-of-month||1-31||, - * ? / L W|
|Month||1-12 or JAN-DEC||, - * /|
|Day-of-week||1-7 or SUN-SAT||, - * ? / L #|
|Year (Optional)||Empty, 1970-2199||, - * /|
Each field allows a simple value or a set of values. There are several ways of specifying different values for a field:
The ‘*’ character is used to specify all values. For example, “*” in the minute field means “every minute”.
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.
Support for specifying both a day-of-week and a day-of-month value is not complete (you’ll need to use the ‘?’ character in one of these fields).
The ‘-’ character is used to specify ranges. For example, “10-12” in the hour field means “the hours 10, 11 and 12”.
The ‘,’ character is used to specify additional values. For example “MON,WED,FRI” in the day-of-week field means “the days Monday, Wednesday, and Friday”.
The ‘/’ character is used to specify increments. For example, “0/15” in the seconds field means “the seconds 0, 15, 30, and 45”. And “5/15” in the seconds field means “the seconds 5, 20, 35, and 50”. Specifying ‘*’ before the ‘/’ is equivalent to specifying 0 is the value to start with. Essentially, for each field in the expression, there is a set of numbers that can be turned on or off. For seconds and minutes, the numbers range from 0 to 59. For hours 0 to 23, for days of the month 0 to 31, and for months 1 to 12. The “/” character simply helps you turn on every “nth” value in the given set. Thus “7/6” in the month field only turns on month “7”, it does NOT mean every 6th month, please note that subtlety.
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” means “the last Friday of the month”. You can also specify an offset from the last day of the month, such as “L-3” which would mean the third-to-last day of the calendar month. When using the ‘L’ option, it is important not to specify lists, or ranges of values, as you’ll get confusing/unexpected results.
The ‘W’ character is allowed for the day-of-month field. This character 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”. So, if the 15th is a Saturday, the trigger will fire on Friday the 14th. If the 15th is a Sunday, the trigger will fire on Monday the 16th. If the 15th is a Tuesday, then it will fire on Tuesday the 15th. However if you specify “1W” as the value for day-of-month, and the 1st is a Saturday, the trigger will fire on Monday the 3rd, as it will not ‘jump’ over the boundary of a month’s days. The ‘W’ character can only be specified when the day-of-month is a single day, not a range or list of days.
The ‘L’ and ‘W’ characters can also be combined for the day-of-month expression to yield ‘LW’, which translates to “last weekday of the month”.
The ‘#’ character is allowed for the day-of-week field. This character is used to specify “the nth” XXX day of the month. For example, the value of “6#3” in the day-of-week field means the third Friday of the month (day 6 = Friday and “#3” = the 3rd one in the month). Other examples: “2#1” = the first Monday of the month and “4#5” = the fifth Wednesday of the month. Note that if you specify “#5” and there is not 5 of the given day-of-week in the month, then no firing will occur that month. If the ‘#’ character is used, there can only be one expression in the day-of-week field (“3#1,6#3” is not valid, since there are two expressions).
The legal characters and the names of months and days of the week are not case sensitive.
Overflowing ranges is supported - that is, having a larger number on the left hand side than the right. You might do 22-2 to catch 10 o’clock at night until 2 o’clock in the morning, or you might have NOV-FEB. It is very important to note that overuse of overflowing ranges creates ranges that do not make sense and no effort has been made to determine which interpretation must be chosen. An example would be “0 0 14-6 ? * FRI-MON”.