异常提示org.springframework.orm.hibernate4.HibernateSystemException: identifier of an instance of com.mi.domain.Department was altered from 2 to 1; nested exception is org.hibernate.HibernateException: identifier of an instance of com.mi.domain.Department was altered from 2 to 1

解决方法：在保存操作执行之前要先打破对象之间的关系（外键）