code: public String getErrorAndRequiredClass(UIInput input, String clientId) {
  		String styleClass = "";
  		if (BsfUtils.isLegacyFeedbackClassesEnabled()) {
  			styleClass = FacesMessages.getErrorSeverityClass(clientId);
  		}
  		if (input.isRequired()) {
  			styleClass += " bf-required";
  		} else {
  			Annotation[] readAnnotations = ELTools.readAnnotations(input);
  			if (null != readAnnotations && readAnnotations.length > 0) {
  				for (Annotation a : readAnnotations) {
  					if ((a.annotationType().getName().endsWith("NotNull"))
  							|| (a.annotationType().getName().endsWith("NotEmpty"))
  							|| (a.annotationType().getName().endsWith("NotBlank"))) {
  						styleClass += " bf-required";
  						break;
  					}
  				}
  			}
  		}
  		return styleClass;
  	}
docs: Yields the value of the required and error level CSS class.
  
  @param input
  must not be null
  @param clientId
  must not be null
  @return can never be null