Package org.camunda.bpm.engine.impl.calendar

Class CronExpression

java.lang.Object
org.camunda.bpm.engine.impl.calendar.CronExpression
All Implemented Interfaces:
Serializable, Cloneable
public class CronExpression extends Object implements Serializable, 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". 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.

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".

Author:
Sharada Jambula, James House, Contributions from Mads Henderson, Refactoring from CronTrigger to CronExpression by Aaron Craven
See Also:

  • Field Details

    • SECOND

      protected static final int SECOND
      See Also:

    • MINUTE

      protected static final int MINUTE
      See Also:

    • HOUR

      protected static final int HOUR
      See Also:

    • DAY_OF_MONTH

      protected static final int DAY_OF_MONTH
      See Also:

    • MONTH

      protected static final int MONTH
      See Also:

    • DAY_OF_WEEK

      protected static final int DAY_OF_WEEK
      See Also:

    • YEAR

      protected static final int YEAR
      See Also:

    • ALL_SPEC_INT

      protected static final int ALL_SPEC_INT
      See Also:

    • NO_SPEC_INT

      protected static final int NO_SPEC_INT
      See Also:

    • ALL_SPEC

      protected static final Integer ALL_SPEC

    • NO_SPEC

      protected static final Integer NO_SPEC

    • monthMap

      protected static final Map monthMap

    • dayMap

      protected static final Map dayMap

    • seconds

      protected transient TreeSet<Integer> seconds

    • minutes

      protected transient TreeSet<Integer> minutes

    • hours

      protected transient TreeSet<Integer> hours

    • daysOfMonth

      protected transient TreeSet<Integer> daysOfMonth

    • months

      protected transient TreeSet<Integer> months

    • daysOfWeek

      protected transient TreeSet<Integer> daysOfWeek

    • years

      protected transient TreeSet<Integer> years

    • lastdayOfWeek

      protected transient boolean lastdayOfWeek

    • nthdayOfWeek

      protected transient int nthdayOfWeek

    • lastdayOfMonth

      protected transient boolean lastdayOfMonth

    • nearestWeekday

      protected transient boolean nearestWeekday

    • lastdayOffset

      protected transient int lastdayOffset

    • expressionParsed

      protected transient boolean expressionParsed

    • MAX_YEAR

      public static final int MAX_YEAR

  • Constructor Details

    • CronExpression

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

  • Method Details

    • getTimeZone

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

    • toString

      public String toString()
      Returns the string representation of the CronExpression
      Overrides:
      toString in class Object
      Returns:
      a string representation of the CronExpression

    • buildExpression

      protected void buildExpression(String expression) throws ParseException
      Throws:
      ParseException

    • storeExpressionVals

      protected int storeExpressionVals(int pos, String s, int type) throws ParseException
      Throws:
      ParseException

    • checkNext

      protected int checkNext(int pos, String s, int val, int type) throws ParseException
      Throws:
      ParseException

    • skipWhiteSpace

      protected int skipWhiteSpace(int i, String s)

    • findNextWhiteSpace

      protected int findNextWhiteSpace(int i, String s)

    • addToSet

      protected void addToSet(int val, int end, int incr, int type) throws ParseException
      Throws:
      ParseException

    • getSet

      protected TreeSet<Integer> getSet(int type)

    • getValue

      protected org.camunda.bpm.engine.impl.calendar.ValueSet getValue(int v, String s, int i)

    • getNumericValue

      protected int getNumericValue(String s, int i)

    • getMonthNumber

      protected int getMonthNumber(String s)

    • getDayOfWeekNumber

      protected int getDayOfWeekNumber(String s)

    • getTimeAfter

      public Date getTimeAfter(Date afterTime)

    • setCalendarHour

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

    • isLeapYear

      protected boolean isLeapYear(int year)

    • getLastDayOfMonth

      protected int getLastDayOfMonth(int monthNum, int year)