Hibernate 关联映射之---- 一对一双向映射

public class IdCard {

// 身份证号(主键)
private String cardNum;// 对象唯一表示(Object Identified, OID)
private String place; //  身份证地址
// 身份证与用户，一对一的关系
private User user;
}

public class User {

private int userId;
private String userName;
// 用户与身份证信息， 一对一关系
private IdCard idCard;
}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="edu.cczu.one2one2">

<class name="IdCard" table="t_IdCard">
<id name="cardNum">
<generator class="assigned"></generator>
</id>
<property name="place" length="20"></property>

<!--
一对一映射，有外键方
unique="true"   给外键字段添加唯一约束
-->
<many-to-one name="user" unique="true" column="user_id" class="User" cascade="save-update"></many-to-one>

</class>

</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="edu.cczu.one2one1">

<class name="User" table="t_user">
<id name="userId">
<generator class="native"></generator>
</id>
<property name="userName" length="20"></property>
<!--
一对一映射： 没有外键方
-->
<one-to-one name="idCard" class="IdCard"></one-to-one>

</class>

</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="edu.cczu.one2one2">

<class name="IdCard" table="t_IdCard">
<id name="user_id">
<!--
id 节点指定的是主键映射, 即user_id是主键
主键生成方式： foreign  即把别的表的主键作为当前表的主键；
property (关键字不能修改)指定引用的对象     对象的全名 cn..User、  对象映射 cn.User.hbm.xml、   table(id)
-->
<generator class="foreign">
<param name="property">user</param>
</generator>
</id>
<property name="cardNum" length="20"></property>
<property name="place" length="20"></property>

<!--
一对一映射，有外键方
（基于主键的映射）
constrained="true"  指定在主键上添加外键约束
-->
<one-to-one name="user" class="User" constrained="true"  cascade="save-update"></one-to-one>

</class>

</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="edu.cczu.one2one2">

<class name="User" table="t_user">
<id name="userId">
<generator class="native"></generator>
</id>
<property name="userName" length="20"></property>
<!--
一对一映射： 没有外键方
-->
<one-to-one name="idCard" class="IdCard"></one-to-one>

</class>

</hibernate-mapping>