code: @Override
      public MessageResourcesGateway getMessageResourceGateway() {
          final MessageResourcesGateway gateway = messageResourcesHolder.getGateway();
          if (gateway == null) {
              String msg = "Not found the gateway for message resource: holder=" + messageResourcesHolder;
              throw new IllegalStateException(msg);
          }
          return gateway;
      }
docs: =================