Hibernate中映射自然外键

Hibernate开发中，通常都是用id来做代理主键，来屏蔽主键与业务的关系。

例如下面学生与班级的ORM

SQL：

create table classes

(

   id                      int(32)      unsigned       not null default '0',

   cla_no                         varchar(10)                    not null,

   cla_name                       varchar(50),

   primary key (id)

)

type = InnoDB;

alter table classes add constraint cla_no_unique unique (cla_no);

 

 

create table student

(

   id                    int(32)         unsigned      not null default '0',

   stu_no                         varchar(20)                    not null,

   stu_name                       varchar(30),

   stu_sex                        char(2),

   stu_age                        int(3),

   stu_address                    varchar(100),

   stu_class                      varchar(10),

   primary key (id)

)

type = InnoDB;

alter table student add constraint stu_no_unique unique(stu_no);

alter table student add constraint FK_Reference_1 foreign key (stu_class)

      references classes (cla_no);

classes(cla_no)作为student(stu_class)的外键

 

关系映射文件

1.    student.hbm.xml

<hibernate-mapping>

    <class name="pojos.Student" table="student" catalog="hibernate">

        <id name="id" type="integer">

            <column name="id" />

            <generator class="hilo" />

        </id>

        <many-to-one name="classes" class="pojos.Classes" fetch="select" cascade="all" lazy="false" property-ref="claNo">

            <column name="stu_class" length="10" />

        </many-to-one>

        <property name="stuNo" type="string">

            <column name="stu_no" length="20" not-null="true" unique="true" />

        </property>

        <property name="stuName" type="string">

            <column name="stu_name" length="30" />

        </property>

。。。。。。。。。

2.    classes.hbm.xml

<hibernate-mapping>

    <class name="pojos.Classes" table="classes" catalog="hibernate">

        <id name="id" type="integer">

            <column name="id" />

            <generator class="hilo" />

        </id>

        <property name="claNo" type="string">

            <column name="cla_no" length="10" not-null="true" unique="true" />

        </property>

        <property name="claName" type="string">

            <column name="cla_name" length="50" />

        </property>

        <set name="students" inverse="true">

            <key property-ref="claNo">

                <column name="stu_class" length="10"/>

            </key>

            <one-to-many class="pojos.Student" />

    </set>

 

POJO属性:

Student.java

    private Integer id;

    private Classes classes;

    private String stuNo;

    private String stuName;

    private String stuSex;

    private Integer stuAge;

Classes.java