Spring update all entity with save - spring-boot

Question

Good morning everyone,
I am trying to update an entity completely through its id, I am using a repository that extends from JPA, I think that just by making it save the system it would crush the old one but it is not like that, I am getting this error:
org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect)
I have tried to use entityManager.flush (); but I get an error:
javax.persistence.TransactionRequiredException: No EntityManager with actual transaction available for current thread - cannot reliably process 'flush' call
I have found options to update a database field but what I really want is to crush the database row completely, is it that complicated? How should I do it? Should I delete the record and recreate it? (I am not convinced because we are generating two transitions but I do not know if it is normal or not)
I put the code responsible for modifying the entity:
#PostMapping ("/ user")
public ResponseEntity postUser (#RequestBody User user) {
Map <Object, Object> model = new HashMap <> ();
entityManager.flush ();
User newUSer = userRepository.saveAndFlush (user);
model.put ("user", newUSer);
return ok (model);
}
Thank you!

Answer 1

Ok, after some test accounts I have found how to make it work correctly, I am doing something wrong, since when I make this code I get it correctly:
#PostMapping ("/ user")
public ResponseEntity postUser (#RequestBody User user) {
Map <Object, Object> model = new HashMap <> ();
AtomicReference <ResponseEntity> responseEntity = new AtomicReference <> ();
Optional <User> optionalUser = Optional.of (userRepository.findById (user.getId ()). Get ());
OptionalConsumer.of (optionalUser) .ifPresent (u -> {
u.setPassword (user.getPassword ());
userRepository.save (u);
model.put ("user", u);
responseEntity.set (ok (model));
}). ifNotPresent (() -> responseEntity.set (notFound (). build ()));
return responseEntity.get ();
}
So what I'm going to do is create a merge method in the User model to modify the data passed by parameter and save it correctly (I'm open to a better way, there may be more recommended ways to work, tell me please!)