EJB 3.1 Cookbook

Understanding calendar-based scheduling

Calendar-based scheduling is used with the @Schedule annotation and with the ScheduleExpression class. It provides an alternative approach for specifying the time when a callback should be made. The calendar-based timer expressions are similar to those used by the UNIX Cron facility.

Using a calendar expression we can express one of several types of events:

• A single event in time
• A repeating set of times
• A time interval

This approach provides a more powerful technique for expressing a point in time.

Getting ready

A calendar expression can be expressed using the @Schedule annotation or using a ScheduleExpression object. These two approaches are closely related. In fact, the Timer class has an isCalendarTimer and ...