2016年5月17日 | Leave a comment 问题: 代码如下,e1.getId() 不行 EntityManager em = **** EntityTransaction trans = em.getTransaction(); trans.begin(); em.persistence(e1); System.out.println(e1.getId());//not work e1. getId() is null e2.referId=e1.getId(); em.persistence(e2); trans.commit(); 12345678 EntityManager em = ****EntityTransaction trans = em.getTransaction();trans.begin();em.persistence(e1);System.out.println(e1.getId());//not work e1. getId() is nulle2.referId=e1.getId();em.persistence(e2);trans.commit(); 解决: em.persistence(e1); 后增加 em.flush() 更新到数据库中