code: public <T> void serviceClass(Class<T> serviceClass)
    {
      if (Vault.class.isAssignableFrom(serviceClass)) {
        _validatorVault.vaultClass(serviceClass);
      }
      else {
        validateServiceClass(serviceClass);
      }
      
      if (Modifier.isAbstract(serviceClass.getModifiers())
          && ! abstractMethods(serviceClass)) {
        throw error(L.l("abstract service class '{0}' is invalid because the abstract methods can't be generated.",
                        serviceClass.getName()));
      }
      
      serviceMethods(serviceClass);
    }
docs: {@code Web.service(Class)} validation