hibernate 一对一

双向一对一，有2种实现方式：

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例如：人（Person）和护照（Passwort）的关系是一对一的的关系：
  1）共享主键的形式：
  1）主表映射文件的写法：
  <class name="Person" table="t_person">
  <id name="id" column="p_id">
  <generator class="increment"></generator>
  </id>
  <property name="name" column="p_name" type="string"></property>
<property name="birthday" column="p_birthday" type="date"></property>
<property name="email" column="email" type="string"></property>
<property name="phone" column="phone" type="string"></property>
<one-to-one name="passport" cascade="all"></one-to-one>
  </class>

  2)辅表映射文件的写法：
  <class name="Passport" table="t_passport">
  <id name="id" column="p_id">
  <generator class="foreign">
  <param name="property">person</param> //person为Passport中的关系属性
  </generator>
  </id>
  <property name="serial" column="p_serial" type="string"></property>
<property name="expiry" column="p_expiry" type="integer"></property>
<property name="date" column="p_date" type="date"></property>
<one-to-one name="person" constrained="true" cascade="all">
</one-to-one>
  </class>

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2)独立外键的关联方式： 
  1）主表映射文件的写法： 
  <class name="Person" table="t_person"> 
  <id name="id" column="p_id"> 
  <generator class="increment"> </generator> 
  </id> 
  <property name="name" column="p_name" type="string"> </property> 
<property name="birthday" column="p_birthday" type="date"> </property> 
<property name="email" column="email" type="string"> </property> 
<property name="phone" column="phone" type="string"> </property> 
<one-to-one name="passport" class="Passport" property-ref="person" cascade="all"> </one-to-one> //person为 
  实体类Passwort中的关系属性。  person是Passport.java类中的一个对象；
  </class> 

  2)辅表映射文件的写法： 
  <class name="Passport" table="t_passport"> 
  <id name="id" column="p_id"> 
  <generator class="increment">  
  </generator> 
  </id> 
  <property name="serial" column="p_serial" type="string"> </property> 
<property name="expiry" column="p_expiry" type="integer"> </property> 
<property name="date" column="p_date" type="date"> </property> 
<many-to-one   name="person" class="Person" column="pss_id" unique="true">//pss_id为外键列 
</one-to-one> 
  </class>