public abstract CronTab getCronTab() throws ANTLRException;
@Override
public long getRecurrencePeriod() {
try {
CronTab tab = getCronTab();
GregorianCalendar now = new GregorianCalendar();
Calendar nextExecution = tab.ceil(now.getTimeInMillis());
long period = nextExecution.getTimeInMillis() - now.getTimeInMillis();
if(nextExecution.getTimeInMillis() - now.getTimeInMillis()<=60000)
period = period + 60000l; //add one minute to not shedule it during one minute one than once
return period;
} catch (Exception ex) {