Retrieve an object and save as new one with Hibernate/Spring Data JPA

Question

In one of the services we perform some operations:

1. Update table A - call method with annotated query, method from repository, which extends JpaRepository.
2. Select from table B (repository.findOne(B_PK))
3. Modify retrieved object from point 2
4. Save modified object as a new entity (repository.save(B_Object))

Unfortunately, we are getting an error: "identifier of an instance of B_Object altered from X to Z". How we should do this in correct way??

Answer 1

您应该像在新实体一样进行更改和存储之前，分离在第2点中获取的对象。

Answer 2

Erase the unique identifier from the object (if it's auto-generated)

If doesnt have a autogen key you need to remove the constraints for the composite key.