Package org.drools.core.time.impl

Class CronExpression

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable
    public class CronExpression
extends KieCronExpression
implements java.lang.Cloneable
    Provides a parser and evaluator for unix-like cron expressions. Cron expressions provide the ability to specify complex time combinations such as "At 8:00am every Monday through Friday" or "At 1:30am every last Friday of the month".

    Cron expressions are comprised of 6 required fields and one optional field separated by white space. 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   , - * /

    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.

    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". When using the 'L' option, it is important not to specify lists, or ranges of values, as you'll get confusing 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.

    NOTES:

    • 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).
    • 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 don't make sense and no effort has been made to determine which interpretation CronExpression chooses. An example would be "0 0 14-6 ? * FRI-MON".

    See Also:
    Serialized Form

    • Constructor Detail

      • CronExpression

        public CronExpression​(java.lang.String cronExpression)
               throws java.text.ParseException
        Constructs a new CronExpression based on the specified parameter.
        Parameters:
        cronExpression - String representation of the cron expression the new object should represent
        Throws:
        java.text.ParseException - if the string expression cannot be parsed into a valid CronExpression

    • Method Detail

      • isSatisfiedBy

        public boolean isSatisfiedBy​(java.util.Date date)
        Indicates whether the given date satisfies the cron expression. Note that milliseconds are ignored, so two Dates falling on different milliseconds of the same second will always have the same result here.
        Parameters:
        date - the date to evaluate
        Returns:
        a boolean indicating whether the given date satisfies the cron expression

      • getNextValidTimeAfter

        public java.util.Date getNextValidTimeAfter​(java.util.Date date)
        Returns the next date/time after the given date/time which satisfies the cron expression.
        Parameters:
        date - the date/time at which to begin the search for the next valid date/time
        Returns:
        the next valid date/time

      • getNextInvalidTimeAfter

        public java.util.Date getNextInvalidTimeAfter​(java.util.Date date)
        Returns the next date/time after the given date/time which does not satisfy the expression
        Parameters:
        date - the date/time at which to begin the search for the next invalid date/time
        Returns:
        the next valid date/time

      • getTimeZone

        public java.util.TimeZone getTimeZone()
        Returns the time zone for which this CronExpression will be resolved.

      • setTimeZone

        public void setTimeZone​(java.util.TimeZone timeZone)
        Sets the time zone for which this CronExpression will be resolved.

      • getTimeAfter

        protected java.util.Date getTimeAfter​(java.util.Date afterTime)

      • setCalendarHour

        protected void setCalendarHour​(java.util.Calendar cal,
                               int hour)
        Advance the calendar to the particular hour paying particular attention to daylight saving problems.
        Parameters:
        cal -
        hour -

      • getTimeBefore

        protected java.util.Date getTimeBefore​(java.util.Date endTime)
        NOT YET IMPLEMENTED: Returns the time before the given time that the CronExpression matches.

      • getFinalFireTime

        public java.util.Date getFinalFireTime()
        NOT YET IMPLEMENTED: Returns the final time that the CronExpression will match.

      • isLeapYear

        protected boolean isLeapYear​(int year)

      • getLastDayOfMonth

        protected int getLastDayOfMonth​(int monthNum,
                                int year)

      • clone

        public java.lang.Object clone()
        Overrides:
        clone in class java.lang.Object