Saving current user id in repository - symfony

Question

I try to save initial value for user field in UserService entity. The reason is, I use this entity in EasyAdminBundle and when I build a form, I want to set a default value for user_id (ManyToOne to User entity).
init entity manager in constructor,
I override save method.
I get user from security session context and set to user service object, persist and flush.
...but I still can't see a change during save.
class UserServiceRepository extends ServiceEntityRepository
{
protected $_em;
public function __construct(RegistryInterface $registry)
{
$this->_em = $this->entityManager;
parent::__construct($registry, UserService::class);
}
// I override save method:
public function save(UserService $userService)
{
// Get current user from security:
$user = $this->get('security.token_storage')->getToken()->getUser();
// set to useService...
$userService->setUser($user);
// and persist & flush:
$this->_em->persist($userService);
$this->_em->flush();
}

Answer 1

// I override save method:
You're overriding non-existent method in parent, there's no save method in ServiceEntityRepository nor EntityRepository. So what's the main point of what you are doing and why you're setting default user_id in service repository?
UPDATE:
services:
my.listener:
class: UserServiceListener
arguments:
- "#security.token_storage"
tags:
- { name: doctrine.event_listener, event: prePersist }
Listener:
class UserServiceListener
{
private $token_storage;
public function __construct(TokenStorageInterface $token_storage)
{
$this->token_storage = $token_storage;
}
public function prePersist(LifeCycleEventArgs $args)
{
$entity = $args->getEntity();
if (!$entity instanceof UserService) {
return;
}
$entity->setUser($this->token_storage->getToken()->getUser());
}
}