Prince Hero

This will help you! I hope

When it is Bidirectional ! Parent class primary key and child class primary key should be same if child class is sharing the Parent's class primary key !
Otherwise you will get

different object with the same identifier value was already associated with the session

If you want update then you have to set same primary to parent and child classes!
So please review mapped entities whether they are having same primary key before hitting the save().

@Autowired ParentRepo parentRepo; @Autowired ChildRepo childRepo; public Parent saveorupdateJPAStyle(Parent parent) {                  parent.getChild().setId(1021); // on the this update should happen (important)                  parent.getChild().setName("Prince007"); //did some update on child                  parent.getAccountDetail().setParent(parent); // setting up the parent to child because it's uni directional                  parent.setStrId(1021); // on the this update should happen  (important)                  parent.setStatus("saved"); // did some update on parent return parentRepo.save(parent); }