JPA EntiityManager.refresh方法

refresh 方法

• 刷新：将数据库中的数据刷新到Managed状态的实体中

refresh 方法测试

find 之后 setter 之后 refresh

@Test
public void test() {
    EntityManagerFactory factory = Persistence.createEntityManagerFactory("myJpa");
    EntityManager em = factory.createEntityManager();
    EntityTransaction tx = em.getTransaction();
    tx.begin();

    Student s = em.find(Student.class, 1L);
    /*

    Hibernate:
        select
            student0_.sid as sid1_0_0_,
            student0_.sage as sage2_0_0_,
            student0_.sname as sname3_0_0_
        from
            Student student0_
        where
            student0_.sid=?

     */
    System.out.println(s); // Student{sid=1, sname='刘备', sage=23}
    s.setSname("陈宫");
    System.out.println(s); // Student{sid=1, sname='陈宫', sage=23}
    em.refresh(s);
    /*

    Hibernate:
        select
            student0_.sid as sid1_0_0_,
            student0_.sage as sage2_0_0_,
            student0_.sname as sname3_0_0_
        from
            Student student0_
        where
            student0_.sid=?

     */
    System.out.println(s); // Student{sid=1, sname='刘备', sage=23}

    tx.commit();
    em.close();
    factory.close();
}