code: static synchronized BeanFactoryId register(Class<?> clazz, Set<String> pathParams,
                                                 List<RequestObjectResolver> objectResolvers) {
          final BeanFactoryId beanFactoryId = new BeanFactoryId(clazz, pathParams);
          if (!factories.containsKey(beanFactoryId)) {
              final AnnotatedBeanFactory<Object> factory = createFactory(beanFactoryId, objectResolvers);
              if (factory != null) {
                  factories.put(beanFactoryId, factory);
                  logger.debug("Registered a bean factory: {}", beanFactoryId);
              } else {
                  factories.put(beanFactoryId, unsupportedBeanFactory);
              }
          }
          return beanFactoryId;
      }
docs: Returns a {@link BeanFactoryId} of the specified {@link Class} and {@code pathParams} for finding its
  factory from the factory cache later.