Triggers allow application developers to plug in rules for when and how often a task should run. The trigger can be as simple as a single, absolute date-time or can include Java™ EE business calendar logic. A Trigger implementation is created by the application developer (or may be supplied to the application externally) and is registered with a task when it is submitted to a ManagedScheduledExecutorService using any of the schedule methods. Each method will run with unspecified context. The methods can be made contextual through creating contextual proxy objects using ContextService.

Each Trigger instance will be invoked within the same process in which it was registered.

Example:

/**
 * A trigger that only returns a single date.
 */
 public class SingleDateTrigger implements Trigger {
     private Date fireTime;

     public TriggerSingleDate(Date newDate) {
         fireTime = newDate;
     }

     public Date getNextRunTime(
        LastExecution lastExecutionInfo, Date taskScheduledTime) {

        if(taskScheduledTime.after(fireTime)) {
            return null;
        }
        return fireTime;
     }

     public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) {
         return scheduledRunTime.after(fireTime);
     }
 }

/**
 * A fixed-rate trigger that will skip any runs if
 * the latencyAllowance threshold is exceeded (the task
 * ran too late).
 */
 public class TriggerFixedRateLatencySensitive implements Trigger {
     private Date startTime;
     private long delta;
     private long latencyAllowance;

     public TriggerFixedRateLatencySensitive(Date startTime, long delta, long latencyAllowance) {
         this.startTime = startTime;
         this.delta = delta;
         this.latencyAllowance = latencyAllowance;
     }

     public Date getNextRunTime(LastExecution lastExecutionInfo, 
                                Date taskScheduledTime) {
         if(lastExecutionInfo==null) {
             return startTime;
         }
         return new Date(lastExecutionInfo.getScheduledStart().getTime() + delta);
     }

     public boolean skipRun(LastExecution lastExecutionInfo, Date scheduledRunTime) {
         return System.currentTimeMillis() - scheduledRunTime.getTime() > latencyAllowance;
     }
 }