同样是Student extends User, Teacher extends User
也许有人会有疑问，这种和每一个具体类一张表的映射策略有什么区别呢？他们的区别在于对每个类一张表的映射策略建立在所有的表是独立的，每个表都包括了子类所自定义的属性和父类继承的属性
而采取每个字类一张表的映射策略，子类所对应的表只包括子类所自定义的属性，而子类所对应的表鱼的父类所对应的表通过FK来关联，也就是说，当持久化子类是，需要在父类和子类中各增加一条记录，这两个记录通过FK关联
< class table ="USERINFO" name ="cn.hxex.exam.model.User" > < id name ="id" column ="ID" > < generator class ="uuid.hex" /> </ id > < property name ="name" column ="NAME" /> < property name ="password" column ="PASSWORD" /> < property name ="fullname" column ="FULLNAME" /> < joined-subclass name ="cn.hxex.exam.model.Student" table ="student" > < key column ="ID" > < many-to-one column ="CLASS_ID" cascade ="save-update" name ="classes" /> </ joined-subclass > < joined-subclass name ="cn.hxex.exam.model.Student" table ="student" > < key column ="ID" > < set cascade ="all" lazy ="true" table ="TEACHER_CLASS" name ="classes" > < key column ="TEACHER_ID" /> < many-to-many class ="cn.hxex.exam.model.Classes" column ="CLASS_ID" /> </ set > </ joined-subclass > </ class >
