Hibernate的unique="true"无效

Question

小弟最近研究hibernate，遇到下面的迷惑，请大虾指教下<hibernate-mapping>
  <class name="ssj.Person" table="PERSON" schema="SSJ">
  <id name="personid" type="java.lang.Integer">
  <column name="PERSONID" precision="22" scale="0" />
  <generator class="assigned"></generator>
  </id>
  <many-to-one name="addressid" column="ADDRESSID" class="ssj.Address"
  unique="true" not-null="true">
  </many-to-one>
  </class>
</hibernate-mapping>Test类
Address add=new Address();
Person per1=new Person();
Person per2=new Person();
add.setAddressid(1);
per1.setPersonid(11);
per2.setPersonid(12);
per1.setAddressid(add);
per2.setAddressid(add);
Session se=HibernateSessionFactory.getSession();
Transaction tx=se.beginTransaction();
se.save(add);
se.save(per1);
se.save(per2);
tx.commit();
se.close();为什么执行能通过？<many-to-one name="addressid" column="ADDRESSID" class="ssj.Address"
  unique="true" not-null="true">
</many-to-one>
中已经指明了unique="true"，为什么不报唯一值约束的错误？

Answer 1

se.save(add);
se.save(per1);
se.save(per2);只会处理se.save(per2); 这就是 事物的概念

Answer 2

<many-to-one name="addressid" column="ADDRESSID" class="ssj.Address"
  unique="true" not-null="true">
</many-to-one>你约束的是add

Answer 3

se.save(add);se.save(per1);se.save(per2);只会处理se.save(per2); 这就是 事物的概念unique用法错误?