JPA - EntityManager.detach Examples

    private static void findAndDetachEntity() {
        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));
        em.close();
    }

    private static void findByReferenceAndDetachEntity() {
        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));
        em.close();
    }

    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();
    }

   private static void persistEmployee() {
        Employee employee = new Employee("Joe", "IT",
                Phone.cell("111-111-1111"), Phone.work("222-222-2222"));
        entityManager.getTransaction().begin();
        entityManager.persist(employee);
        entityManager.getTransaction().commit();
        //detach to remove it from entityManager cache
        entityManager.detach(employee);
    }