static Class _getAttributeType(String attName) {
    ConfigAttribute ca = attributes.get(attName);
    if (ca == null) {
      if (attName.startsWith(SECURITY_PREFIX) || attName.startsWith(SSL_SYSTEM_PROPS_NAME)
          || attName.startsWith(SYS_PROP_NAME)) {
        return String.class;
      }
      throw new InternalGemFireException(
          String.format("unhandled attribute name %s.",
              attName));
    }
    return ca.type();
  }
child class can override this method to return a list of unModifiable attributes no matter what
the default is

@return an empty list
geode-core/src/main/java/org/apache/geode/distributed/internal/AbstractDistributionConfig.java