JPA - EntityManager.merge Examples

    private static void updateEmployee(Employee employee) {
        System.out.println("-- merging employee --");
        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();
        em.merge(employee);
        em.getTransaction().commit();
        print("Employee merged", employee);
    }

    private static List<Phone> mergeAndGetPhoneList(Person person) {
        EntityManager em = emf.createEntityManager();
        person = em.merge(person);
        List<Phone> phoneList = person.getPhoneList();
        em.close();
        return phoneList;
    }

    private static void findDetachAndMergeEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.find(Employee.class, 1);
        System.out.println("after find(): " + em.contains(employee));
        em.detach(employee);
        System.out.println("after detach(): " + em.contains(employee));
        employee = em.merge(employee);
        System.out.println("after merging(): " + em.contains(employee));
        em.close();
    }

    private static void findByRefDetachAndMerge() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.getReference(Employee.class, 1);
        System.out.println("after getReference(): " + em.contains(employee));
        em.detach(employee);
        System.out.println("after detach(): " + em.contains(employee));
        employee = em.merge(employee);
        System.out.println("after merge(): " + em.contains(employee));
        em.close();
    }