code: public <T> void includeClass(Class<T> includeClass)
    {
      Objects.requireNonNull(includeClass);
  
      validateIncludeClass(includeClass);
  
      if (includeClass.isAnnotationPresent(Service.class)) {
        serviceClass(includeClass);
      }
  
      if (! includeIsActive(includeClass)) {
        throw new IllegalArgumentException(L.l("include class '{0}' is invalid because it does not define any beans, services, or paths.",
                                               includeClass.getName()));
      }
    }
docs: {@code Web.include(Class)} class validation