code: private UserRegistry getUserRegistryFromConfiguration() throws RegistryException {
          String[] refIds = this.refId;
          if (refIds == null || refIds.length == 0) {
              // Can look for config.source = file
              // If thats set, and we're missing this, we can error.
              // If its not set, we don't have configuration from the
              // file and we should try to resolve if we have one instance defined?
              Tr.error(tc, "USER_REGISTRY_SERVICE_CONFIG_ERROR_NO_REFID");
              throw new RegistryException(TraceNLS.getFormattedMessage(
                                                                       this.getClass(),
                                                                       TraceConstants.MESSAGE_BUNDLE,
                                                                       "USER_REGISTRY_SERVICE_CONFIG_ERROR_NO_REFID",
                                                                       null,
                                                                       "CWWKS3000E: A configuration error has occurred. There is no configured refId parameter for the userRegistry configuration."));
          } else if (refIds.length == 1) {
              return getUserRegistry(refIds[0]);
          } else {
              // Multiple refIds, we'll use the UserRegistryProxy.
              List<UserRegistry> delegates = new ArrayList<UserRegistry>();
              for (String refId : refIds) {
                  delegates.add(getUserRegistry(refId));
              }
              return new UserRegistryProxy(realm, delegates);
          }
      }
docs: When a configuration element is defined, use it to resolve the effective
  UserRegistry configuration.
  
  @return
  @throws RegistryException