public static List<String> getQueryStringParameterValues(HttpServletRequest request, String parameterName) {
    MultiValueMap<String, String> valueMap = getQueryStringParameters(request);
    return ((valueMap == null) || !valueMap.containsKey(parameterName))
        ? null
        : valueMap.get(parameterName);
  }
Returns a {@link List} of values parsed from the request's query string for the given parameter
name.

@param request the {@link HttpServletRequest}
@return a List of values for the specified query parameter; or <code>null</code> if the
requested parameter is not present
@see #getQueryStringParameters(HttpServletRequest)
ambari-server/src/main/java/org/apache/ambari/server/utils/RequestUtils.java