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:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected static Integer	ALL_SPEC
protected static int	ALL_SPEC_INT
protected static int	DAY_OF_MONTH
protected static int	DAY_OF_WEEK
protected static Map	dayMap
protected TreeSet<Integer>	daysOfMonth
protected TreeSet<Integer>	daysOfWeek
protected boolean	expressionParsed
protected static int	HOUR
protected TreeSet<Integer>	hours
protected int	lastdayOffset
protected boolean	lastdayOfMonth
protected boolean	lastdayOfWeek
static int	MAX_YEAR
protected static int	MINUTE
protected TreeSet<Integer>	minutes
protected static int	MONTH
protected static Map	monthMap
protected TreeSet<Integer>	months
protected boolean	nearestWeekday
protected static Integer	NO_SPEC
protected static int	NO_SPEC_INT
protected int	nthdayOfWeek
protected static int	SECOND
protected TreeSet<Integer>	seconds
protected static int	YEAR
protected TreeSet<Integer>	years

Constructor Summary

Constructors

Constructor and Description
CronExpression(String cronExpression) Constructs a new CronExpression based on the specified parameter.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	addToSet(int val, int end, int incr, int type)
protected void	buildExpression(String expression)
protected int	checkNext(int pos, String s, int val, int type)
protected int	findNextWhiteSpace(int i, String s)
protected int	getDayOfWeekNumber(String s)
protected int	getLastDayOfMonth(int monthNum, int year)
protected int	getMonthNumber(String s)
protected int	getNumericValue(String s, int i)
protected TreeSet<Integer>	getSet(int type)
Date	getTimeAfter(Date afterTime)
TimeZone	getTimeZone() Returns the time zone for which this CronExpression will be resolved.
protected org.camunda.bpm.engine.impl.calendar.ValueSet	getValue(int v, String s, int i)
protected boolean	isLeapYear(int year)
protected void	setCalendarHour(Calendar cal, int hour) Advance the calendar to the particular hour paying particular attention to daylight saving problems.
protected int	skipWhiteSpace(int i, String s)
protected int	storeExpressionVals(int pos, String s, int type)
String	toString() Returns the string representation of the CronExpression

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

SECOND

protected static final int SECOND

See Also:

Constant Field Values

MINUTE

protected static final int MINUTE

See Also:

Constant Field Values

HOUR

protected static final int HOUR

See Also:

Constant Field Values

DAY_OF_MONTH

protected static final int DAY_OF_MONTH

See Also:

Constant Field Values

MONTH

protected static final int MONTH

See Also:

Constant Field Values

DAY_OF_WEEK

protected static final int DAY_OF_WEEK

See Also:

Constant Field Values

YEAR

protected static final int YEAR

See Also:

Constant Field Values

ALL_SPEC_INT

protected static final int ALL_SPEC_INT

See Also:

Constant Field Values

NO_SPEC_INT

protected static final int NO_SPEC_INT

See Also:

Constant Field Values

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 Detail

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 Detail

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)