Package cn.boboweike.carrot.scheduling.cron

Class CronExpression

  • All Implemented Interfaces:
    Comparable<Schedule>
    public class CronExpression
extends Schedule
    Schedule class represents a parsed crontab expression.

    The schedule class cannot be instantiated using a constructor, a Schedule object can be obtain by using the static create(java.lang.String) method, which parses a crontab expression and creates a Schedule object.

    Original version https://github.com/asahaf/javacron

    Author:
    Ahmed AlSahaf, Ronald Dehuysser (minor modifications)

    • Method Detail

      • create

        public static CronExpression create​(String expression)
        Parses crontab expression and create a Schedule object representing that expression.

        The expression string can be 5 fields expression for minutes resolution. 

          ┌───────────── minute (0 - 59)
  │ ┌───────────── hour (0 - 23)
  │ │ ┌───────────── day of the month (1 - 31) or L for last day of the month
  │ │ │ ┌───────────── month (1 - 12 or Jan/January - Dec/December)
  │ │ │ │ ┌───────────── day of the week (0 - 6 or Sun/Sunday - Sat/Saturday)
  │ │ │ │ │
  │ │ │ │ │
  │ │ │ │ │
 "* * * * *"

        or 6 fields expression for higher, seconds resolution. 

          ┌───────────── second (0 - 59)
  │ ┌───────────── minute (0 - 59)
  │ │ ┌───────────── hour (0 - 23)
  │ │ │ ┌───────────── day of the month (1 - 31) or L for last day of the month
  │ │ │ │ ┌───────────── month (1 - 12 or Jan/January - Dec/December)
  │ │ │ │ │ ┌───────────── day of the week (0 - 6 or Sun/Sunday - Sat/Saturday)
  │ │ │ │ │ │
  │ │ │ │ │ │
  │ │ │ │ │ │
 "* * * * * *"
        Parameters:
        expression - a crontab expression string used to create Schedule.
        Returns:
        Schedule object created based on the supplied crontab expression.
        Throws:
        InvalidCronExpressionException - if the provided crontab expression is invalid. The crontab expression is considered invalid if it is not properly formed, like empty string or contains less than 5 fields or more than 6 field. It's also invalid if the values in a field are beyond the allowed values range of that field. Non-occurring schedules like "0 0 30 2 *" is considered invalid too, as Feb never has 30 days and a schedule like this never occurs.

      • next

        public Instant next​(Instant createdAtInstant,
                    Instant currentInstant,
                    ZoneId zoneId)
        Calculates the next occurrence based on provided base time.
        Specified by:
        next in class Schedule
        Parameters:
        createdAtInstant - Instant object based on which calculating the next occurrence.
        currentInstant - Instant object used to calculate next occurrence (normally Instant.now()).
        zoneId - the zone for which to calculate the schedule
        Returns:
        Instant of the next occurrence.

      • equals

        public boolean equals​(Object obj)
        Compares this object against the specified object. The result is true if and only if the argument is not null and is a Schedule object that whose seconds, minutes, hours, days, months, and days of weeks sets are equal to those of this schedule.

        The expression string used to create the schedule is not considered, as two different expressions may produce same schedules.

        Overrides:
        equals in class Schedule
        Parameters:
        obj - the object to compare with
        Returns:
        true if the objects are the same; false otherwise

      • isLeapYear

        public static boolean isLeapYear​(int year)

      • getNumberOfFields

        public int getNumberOfFields()

      • getExpression

        public String getExpression()