Interface CronScheduler


  • @NonNullByDefault
    public interface CronScheduler
    The software utility Cron is a time-based job scheduler in Unix-like computer operating systems. People who set up and maintain software environments use cron to schedule jobs (commands or shell scripts) to run periodically at fixed times, dates, or intervals. It typically automates system maintenance or administration—though its general-purpose nature makes it useful for things like connecting to the Internet and downloading email at regular intervals.[1] The name cron comes from the Greek word for time, χρόνος chronos.

    The Unix Cron defines a syntax that is used by the Cron service. A user should register a Cron service with the CronJob.CRON property. The value is according to the Cron.

     * * * * * * *
     | │ │ │ │ │ |
     | │ │ │ │ │ └ year (optional)
     | │ │ │ │ └── day of week from Monday (1) to Sunday (7).
     | │ │ │ └──── month (1 - 12) from January (1) to December (12).
     | │ │ └────── day of month (1 - 31)
     | │ └──────── hour (0 - 23)
     | └────────── min (0 - 59)
     └──────────── sec (0-59)
     
     Field name   mandatory  Values           Special characters
     Seconds      Yes        0-59             * / , -
     Minutes      Yes        0-59             * / , -
     Hours        Yes        0-23             * / , -
     Day of month Yes        1-31             * / , - ? L W
     Month        Yes        1-12 or JAN-DEC  * / , -
     Day of week  Yes        1-7 or MON-SUN   * / , - ? L #
     Year         No         1970–2099        * / , -
     

    Asterisk ( * )

    The asterisk indicates that the cron expression matches for all values of the field. E.g., using an asterisk in the 4th field (month) indicates every month.

    Slash ( / )

    Slashes describe increments of ranges. For example 3-59/15 in the 1st field (minutes) indicate the third minute of the hour and every 15 minutes thereafter. The form "*\/..." is equivalent to the form "first-last/...", that is, an increment over the largest possible range of the field.

    Comma ( , )

    Commas are used to separate items of a list. For example, using "MON,WED,FRI" in the 5th field (day of week) means Mondays, Wednesdays and Fridays. Hyphen ( - ) Hyphens define ranges. For example, 2000-2010 indicates every year between 2000 and 2010 AD, inclusive.

    Additionally, you can use some fixed formats:

     @yearly (or @annually)  Run once a year at midnight on the morning of January 1                      0 0 1 1 *
     @monthly                Run once a month at midnight on the morning of the first day of the month    0 0 1 * *
     @weekly                 Run once a week at midnight on Sunday morning                                0 0 * * 0
     @daily                  Run once a day at midnight                                                   0 0 * * *
     @hourly                 Run once an hour at the beginning of the hour                                0 * * * *
     @reboot                 Run at startup                                                               @reboot
     

    Please note that for the constants we follow the Java 8 Date & Time constants. Major difference is the day number. In Quartz this is 0-6 for SAT-SUN while here it is 1-7 for MON-SUN.

    Author:
    Peter Kriens - Initial contribution, Simon Kaufmann - adapted to CompletableFutures, Hilbrand Bouwkamp - Moved Cron scheduling to it's own interface
    • Method Detail

      • schedule

        ScheduledCompletableFuture<Void> schedule​(CronJob cronJob,
                                                  Map<String,​Object> config,
                                                  String cronExpression)
        Schedule a runnable to be executed for the give cron expression (See CronJob). Every time when the cronExpression matches the current time, the runnable will be run. The method returns a ScheduledCompletableFuture that can be used to stop scheduling. The run method of cronJob takes an environment object. An environment object is a custom interface where the names of the methods are the keys in the properties (see DTOs).
        Type Parameters:
        T - The data type of the parameter for the cron job
        Parameters:
        cronJob - The runnable to run
        cronExpression - A cron expression
        Returns:
        A ScheduledCompletableFuture to cancel the schedule