code: protected static String getSourceParameter(final HttpServletRequest request, final String... paramNames) {
          if (request != null) {
              val parameterMap = request.getParameterMap();
              return Stream.of(paramNames)
                  .filter(p -> parameterMap.containsKey(p) || request.getAttribute(p) != null)
                  .findFirst()
                  .orElse(null);
          }
          return null;
      }
docs: Gets source parameter.
  
  @param request    the request
  @param paramNames the param names
  @return the source parameter