CrudRepository: Save method deletes entry

Question

Calling CrudRepository.save() method deletes entry instead of updating the existing entry.

Controller:

@RequestMapping(value = "{id}", method = PATCH)   
public User update(@PathVariable Long id, @RequestBody UpdateUser existingUser) {
  return userService.update(existingUser);
}

Service:

public User update(UpdateUser existingUser) {
  if (!userRepository.exists(existingUser.getId()) {
    throw new UserNotFoundException();
  }

  UserEntity userEntity = existingUser.toEntity();
  return userRepository.save(userEntity).toDto();
}

Dtos:

public User {
  private Long id;
  private String name;
  // ..

  public UserEntity toEntity() {
    UserEntity entity = new UserEntity();
    entity.setId(id);
    entity.setName(name);
    return entity;
  }
}

public UpdateUser extends User {
  @NotNull
  @Override
  public Long getId() {
    super.getId();
  }
}

I made sure that ID is set on the Dto as it's recieved by the controller & the service and that it's still the same after update. In any case what happens is that service update method appears to save & delete the entity. Because I get back the dto which would have been created from entity returned from save method and I can see the changed name. However if I refresh the page or look into the users table the entry is gone.

Answer 1

You're always creating a new Entity and saving it (in your toEntity() method, which essentially overwrites the previous entity.

If you want to update an existing User, you need to do fetch + update on it's fields, and then invoke save.

for example this will update the name of an existing user:

UserEntity userEntity = userRepository.findOneById(existingUser.getId())
userEntity.setName(newName);
userRepository.save(userEntity);

You should also not set the ID of the entities by hand. Leverage @Id and @GeneratedValue.