code: public static @Nullable String get(@NotNull ServletRequest request, @NotNull String param, @Nullable String defaultValue) {
      String value = request.getParameter(param);
      if (value != null) {
        // convert encoding to UTF-8 if not form encoding parameter is set
        if (!hasFormEncodingParam(request)) {
          value = convertISO88591toUTF8(value);
        }
        return value;
      }
      else {
        return defaultValue;
      }
    }
docs: Returns a request parameter.<br>
  In addition the method fixes problems with incorrect UTF-8 characters returned by the servlet engine.
  All character data is converted from ISO-8859-1 to UTF-8 if not '_charset_' parameter is provided.
  @param request Request.
  @param param Parameter name.
  @param defaultValue Default value.
  @return Parameter value or the default value if it is not set.