code: protected void addRequestParameters(final HttpServletRequest httpServletRequest, final Map<String, List<Object>> attributes) {
          // If a referringParameterName is specified, first match against
          if (referringParameterName != null
                  && StringUtils.isNotBlank(httpServletRequest.getParameter(referringParameterName))) {
              String referringValue = httpServletRequest.getParameter(referringParameterName);
              Map<String, String> referringParameters = parseRequestParameterString(referringValue);
              for (final Map.Entry<String, Set<String>> parameterMapping : parameterAttributeMapping.entrySet()) {
                  final String parameterName = parameterMapping.getKey();
                  final String value = referringParameters.get(parameterName);
  
                  if (value != null) {
                      for (final String attributeName : parameterMapping.getValue()) {
                          attributes.put(attributeName, list(value));
                      }
                  }
              }
          }
          for (final Map.Entry<String, Set<String>> parameterMapping : parameterAttributeMapping.entrySet()) {
              final String parameterName = parameterMapping.getKey();
              final String value = httpServletRequest.getParameter(parameterName);
  
              if (value != null) {
                  for (final String attributeName : parameterMapping.getValue()) {
                      attributes.put(attributeName, list(value));
                  }
              }
          }
      }
docs: Add specified request parameters to the attributes map.  The request parameters may be directly in
  the URL or in a referringUrl parameter (with uPortal accessing /uPortal?nativeClient=true will go through
  several redirects and get turned into /uPortal/Login?refUrl=%2FuPortal%2F%3FnativeClient%3Dtrue,
  which when fetched with request.getParameter(refurl) yields '/uPortal/?nativeClient=true').
  @param httpServletRequest Servlet Request
  @param attributes Map of attributes to add additional attributes to from the Http Request
  @since 1.7.1