一对一唯一外键关联(单向、双向)映射(含测试分析).docxVIP

一对一唯一外键关联映射(单向)?一对唯一外键关联映射是采用多对一关联映射方法来解决一对一的问题，它就是多对一的一个特例。它是基于这样一种思想：在映射多的一端时采用many-to-one标签，并且用属性unique=true来限定它是唯一的，这样就实现了多的一端的多重性为一。但是，它仍保留多対一的痕迹(比如关系模型中增加一个外键字段)。3.实体类：? IdCard.javapublic?class?IdCard {???private?Integer id;???private?String cardNo;?????//一系列的getter.setter方法???@Override???public?String toString() {?????// TODO Auto-generated method stub?????return?Idcard:?+ cardNo;???}?}??? Person.javapublic?class?Person {???private?Integer id;???private?String name;???private?IdCard idCard;???//一系列的setter.getter方法???????@Override???public?String toString() {?????// TODO Auto-generated method stub?????return?Person:?+ name;???}?}4.映射文件：? IdCard.hbm.xml??class?name=com.sxt.hibernate.one2one.entity.IdCard?table=sxt_hibernate_idCard?????id?name=id?length=4???????generator?class=native/generator?????/id?????property?name=cardNo?length=10/property???/class???Person.hbm.xml??class?name=com.sxt.hibernate.one2one.entity.Person?table=sxt_hibernate_person?????id?name=id?length=4???????generator?class=native/generator?????/id?????property?name=name?length=10/property?????!--many-to-one标签的含义,是在本表中增加外键指向另一端。??????????unique=true含义,是本表的本字段加上唯一性约束.??--?????many-to-one?name=idcard_id column=字段?unique=true/many-to-one?!--name为对象成员,若不加column设置表列名，列名将默认为idcard_id--??/class6.测试方法：??public?static?void?main(String[] args) {?????Session session = HibernateUtils.getSession();?????Transaction t = session.beginTransaction();?????try?{???????/**?????????* 测试插入操作?????????*/?/*??????IdCard idCard=new IdCard();???????idCard.setCardNo(1234567890);???????????????Person person=new Person();???????person.setIdCard(idCard);???????//不能成功保存，会报错org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.sxt.hibernate.one2one.entity.IdCard???????//因为idCard是transient状态???????//要在many-to-one中加上cascade=save-update,或者是在session.save(person)之前session.save(idCard)???????session.save(person);*/?????????/*??????IdCard idCard=new