public DataValidatorBuilder isValidRecurringRule(final String recurringRule) {
if (StringUtils.isNotBlank(recurringRule)) {
try {
final RRule rRule = new RRule(recurringRule);
rRule.validate();
} catch (final ValidationException e) {
final ApiParameterError error = ApiParameterError.parameterError("validation.msg.invalid.recurring.rule",
"The Recurring Rule value: " + recurringRule + " is not valid.", this.parameter, recurringRule);
this.dataValidationErrors.add(error);
return this;