Schedule at 24hrs interval

Question

I want to know the best method to schedule a code. I have a code that generates reports and sends mail to a set of people at interval of 24hrs. Its a console based java application. I want to know the best method to schedule that. Sometimes I may need to change that to 12hrs interval. However the application doesn't perform any other task in between the interval.

Answer 1

Here are few approach, from simplest to most comprehensive:

1. sleep():

   TimeUnit.HOURS.sleep(24)
   

   This approach is very simple, do the work and sleep for 24 hours. Actually it is a bit more complex because the report generation takes some time, so you have to sleep slightly shorter. All solutions below handle this transparently.

2. java.util.Timer#scheduleAtFixedRate() - simple, built-in Java solution.

3. @Scheduled annotation in spring or @Schedule in ejb - more complex but also more powerful, e.g. accepts cron expressions:

   @Scheduled(fixedRate=DateUtils.MILLIS_PER_DAY)
   public void generateReport() {
     //...
   }
   

4. quartz-scheduler - full blown Java scheduler with clustering and fail-over, misfire handling, full cron support, etc. Very comprehensive:

   newTrigger().
     withSchedule(
       simpleSchedule().
         withIntervalInHours(24).
         repeatForever()
       ).build();
   

   or

   newTrigger().
     withSchedule(
       cronSchedule().
         dailyAtHourAndMinute(17, 30).  //17:30
       ).build();