code: private Map<String, Set<String>> getParameters(HttpServletRequest request) {
          Map<String, String[]> params = request.getParameterMap();
  
          Map<String, Set<String>> queryParameters = new HashMap<>(params.size());
          for (Map.Entry<String, String[]> entry : params.entrySet()) {
              queryParameters.put(entry.getKey(), new HashSet<>(Arrays.asList(entry.getValue())));
          }
          return queryParameters;
      }
docs: This method return a list o parameters. It uses {@link ServletRequest#getParameterMap()} which can also return POST
  body parameters, but we don't expect to receive such body.
  
  @param request request body
  @path
  @return query parameters