Hibernate——关联关系的CRUD（增删改查）二

（三）改

通过更新user来更新group

@Testpublic void testUpdateUser() {testSaveGroup();Session session = sf.getCurrentSession();session.beginTransaction();User u = (User)session.get(User.class, 1);session.getTransaction().commit();Session session2 = sf.getCurrentSession();session2.beginTransaction();u.getGroup().setName("group");session2.update(u);session2.getTransaction().commit();}

（四）删

@Testpublic void testDelete() {testSaveGroup();Session session = sf.getCurrentSession();session.beginTransaction();User u = (User)session.get(User.class, 1);session.delete(u);session.getTransaction().commit();}

此时数据库中有u1，u2，g1三条数据，删除u1，其他两条也一起被删除了

这是因为user表级联着group表，group表也级联着user表，删了u1就删了g1，删了g1就把g1下所有的user都删了

若只想删除u1，可以把u1与g1的关联关系设为null

或者直接用HQL语句实现

@Testpublic void testDelete() {testSaveGroup();Session session = sf.getCurrentSession();session.beginTransaction();//User u = (User)session.get(User.class, 1);//u.setGroup(null);//session.delete(u);session.createQuery("delete from User u where u.id=1").executeUpdate();session.getTransaction().commit();}