Hibernate关系映射1 ——主键关联映射

主键关联生成的关系模型: (每个员工只属于一个部门)

t_employee(idintpkfk->t_department(id),namevarchar)

t_department(id int pk, name varchar)

1、主键单向关联

实体模型:

com.lrh.hibernate.Employee(intid,Stringname,Departmentdepartment)

com.lrh.hibernate.Department(int id, String name)

配置文件:

<!--com.lrh.hibernate/Employee.hbm.xml-->

<hibernate-mapping>

<classname="com.lrh.hibernate.Employee"table="t_employee">

<idname="id">

<!--采用foreign生成策略,Employee的主键来源Department,forgeign会取得关联对象的标识-->

<generatorclass="foreign">

<!--指定要参照的属性-->

<paramname="property">department</param>

</generator>

</id>

<propertyname="name"/>

<!--one-to-one标签的含义,表明hibernate如何加载它的关联对象,默认是根据主键加载,

constrained="true",表明当前主键上存在一个约束,当前主键(Employee的主键)还是一个外键

参照了对端的主键(Department的主键)

-->

<one-to-onename="department"constrained="true"/>

</class>

</hibernate-mapping>

<!--com.lrh.hibernate/Department.hbm.xml-->

<hibernate-mapping>

<classname="com.lrh.hibernate.Department"table="t_department">

<idname="id"><generatorclass="native"/></id>

<propertyname="name"/>

</class>

 </hibernate-mapping>

2、主键双向关联

实体模型:

com.lrh.hibernate.Employee(intid,Stringname,Departmentdepartment)

com.lrh.hibernate.Department(int id, String name, Employee employee)

配置文件:

<!--com.lrh.hibernate/Employee.hbm.xml-->

<hibernate-mapping>

<classname="com.lrh.hibernate.Employee"table="t_employee">

<idname="id">

<!--指定主键生成策略为外键-->

<generatorclass="foreign">

<!--指定要参照的属性-->

<paramname="property">department</param>

</generator>

</id>

<propertyname="name"/>

<!--使用<one-to-one>映射一对一关系。-->

<one-to-onename="department">

</class>

</hibernate-mapping>

配置文件:

<!--com.lrh.hibernate/Department.hbm.xml-->

<hibernate-mapping>

<classname="com.lrh.hibernate.Department"table="t_department">

<idname="id"><generatorclass="native"/></id>

<propertyname="name"/>

<!--

需要在Department映射文件中加入<one-to-one>标签指向employee,指示hibernate如何加载employee

默认根据主键加载

-->

<one-to-onename="employee"/>

</class>

</hibernate-mapping>

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