Hibernate 多对一外键单向关联

一、模型介绍

 

多个人（Person）对应一个地址（Address）。

 

二、实体（省略getter、setter方法）

 

public class Personn1fk {

    private int personid;

    private String name;

    private int age;

    private Addressn1fk addressn1fk;

 

public class Addressn1fk {

    private int addressid;

    private String addressdetail;

 

三、表模型

 

mysql> desc address_n1kf;

+---------------+--------------+------+-----+---------+----------------+

| Field         | Type         | Null | Key | Default | Extra          |

+---------------+--------------+------+-----+---------+----------------+

| addressid     | int(11)      | NO   | PRI | NULL    | auto_increment |

| addressdetail | varchar(255) | YES  |     | NULL    |                |

+---------------+--------------+------+-----+---------+----------------+

 

mysql> desc person_n1kf;

+-----------+--------------+------+-----+---------+----------------+

| Field     | Type         | Null | Key | Default | Extra          |

+-----------+--------------+------+-----+---------+----------------+

| personid  | int(11)      | NO   | PRI | NULL    | auto_increment |

| name      | varchar(255) | YES  |     | NULL    |                |

| age       | int(11)      | YES  |     | NULL    |                |

| addressId | int(11)      | YES  | MUL | NULL    |                |

+-----------+--------------+------+-----+---------+----------------+

 

四、生成的SQL脚本

 

CREATE TABLE `address_n1kf` (

  `addressid` int(11) NOT NULL auto_increment,

  `addressdetail` varchar(255) default NULL,

  PRIMARY KEY  (`addressid`)

) ENGINE=InnoDB DEFAULT CHARSET=gbk;

 

DROP TABLE IF EXISTS `person_n1kf`;

 

CREATE TABLE `person_n1kf` (

  `personid` int(11) NOT NULL auto_increment,

  `name` varchar(255) default NULL,

  `age` int(11) default NULL,

  `addressId` int(11) default NULL,

  PRIMARY KEY  (`personid`),

  KEY `FK4571AF54A2A3EE48` (`addressId`),

  CONSTRAINT `FK4571AF54A2A3EE48` FOREIGN KEY (`addressId`) REFERENCES `address_n1kf` (`addressid`)

) ENGINE=InnoDB DEFAULT CHARSET=gbk;

 

 

五、映射方法

 

<hibernate-mapping>

    <class name="com.lavasoft.dx._n_1_fk.Personn1fk" table="PERSON_n1fk">

        <id name="personid">

            <generator class="identity"/>

        </id>

        <property name="name"/>

        <property name="age"/>

        <!--用来映射关联PO column是Address在该表中的外键列名-->

        <many-to-one name="addressn1fk" column="addressId"/>

    </class>

</hibernate-mapping>

 

<hibernate-mapping>

    <class name="com.lavasoft.dx._n_1_fk.Addressn1fk" table="ADDRESS_n1fk">

        <id name="addressid">

            <generator class="identity"/>

        </id>

        <property name="addressdetail"/>

    </class>

</hibernate-mapping>

 

 

六、测试方法

 

public class Test_n1fk {

    public static void main(String[] args){

        Personn1fk p1=new Personn1fk();

        Personn1fk p2=new Personn1fk();

 

        p1.setAge(21);

        p1.setName("p1");

 

        p2.setAge(23);

        p2.setName("p2");

 

        Addressn1fk add=new Addressn1fk();

        add.setAddressdetail("郑州市经三路");

 

        p1.setAddressn1fk(add);

        p2.setAddressn1fk(add);

 

        Session session=HibernateUtil.getCurrentSession();

        Transaction tx=session.beginTransaction();

        session.save(add);

        session.save(p1);

        session.save(p2);

        tx.commit();

        HibernateUtil.closeSession();

    }

}

 

七、测试结果

 

1) :正常保存. 推荐这么干!

 

        session.save(p1);

        session.save(p2);

 

Hibernate: insert into ADDRESS_n1kf (addressdetail) values (?)

Hibernate: insert into PERSON_n1kf (name, age, addressId) values (?, ?, ?)

Hibernate: insert into PERSON_n1kf (name, age, addressId) values (?, ?, ?)

 

2) :正常保存.

        session.save(p1);

        session.save(p2);

        session.save(add);

 

Hibernate: insert into PERSON_n1kf (name, age, addressId) values (?, ?, ?)

Hibernate: insert into PERSON_n1kf (name, age, addressId) values (?, ?, ?)

Hibernate: insert into ADDRESS_n1kf (addressdetail) values (?)

Hibernate: update PERSON_n1kf set name=?, age=?, addressId=? where personid=?

Hibernate: update PERSON_n1kf set name=?, age=?, addressId=? where personid=?

 

3) :正常保存.

        session.save(add);

//        session.save(p1);

//        session.save(p2);

 

Hibernate: insert into ADDRESS_n1kf (addressdetail) values (?)

 

4) : 发生异常,不能保存.

//        session.save(add);

        session.save(p1);

        session.save(p2);

Hibernate: insert into PERSON_n1kf (name, age, addressId) values (?, ?, ?)

Hibernate: insert into PERSON_n1kf (name, age, addressId) values (?, ?, ?)

Exception in thread "main" org.hibernate.TransientObjectException: com.lavasoft.dx._n_1_fk.Addressn1kf