Hibernate: How to fix “identifier of an instance altered from X to Y”?

Question

org.hibernate.HibernateException: identifier of an instance 
of org.cometd.hibernate.User altered from 12 to 3

in fact, my user table

Answer 1

If you are using Spring MVC or Spring Boot try to avoid: @ModelAttribute("user") in one controoler, and in other controller model.addAttribute("user", userRepository.findOne(someId);

This situation can produce such error.