protected void initBinder(final HttpServletRequest request, final ServletRequestDataBinder binder) {
        if (serviceValidateConfigurationContext.getCasProperties().getSso().isRenewAuthnEnabled()) {
            binder.setRequiredFields(CasProtocolConstants.PARAMETER_RENEW);
        }
    }
Add validation specification.

@param validationSpecification the validation specification
support/cas-server-support-validation-core/src/main/java/org/apereo/cas/web/AbstractServiceValidateController.java