一对多外键单向关联

Hibernate 一对多外键单向关联

 

    这种情况很少见，但Hibernate同样允许采用连接表关联1-1.有连接表的1-1同样只需要将N-1的many-to-one元素增加unique="true"属性即可。

 

一、模型介绍

 

一个人（Person）对应多个地址（Address），比如家庭地址、公司地址。

 

二、实体（省略getter、setter方法）

 

public class Person1nfk implements Serializable {

    private int personid;

    private String name;

    private int age;

    private Set addresses=new HashSet();

 

public class Address1nfk implements Serializable {

    private int addressid;

    private String addressdetail;

 

三、表模型

 

mysql> desc address_1nfk;

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

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

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

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

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

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

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

 

mysql> desc person_1nfk;

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

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

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

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

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

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

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

 

四、生成的SQL脚本

 

  /* Formatted on 2007/08/21 10:06 (QP5 v5.50) */

  CREATE TABLE `address_1nfk` (

    `addressid` int(11) NOT NULL auto_increment,

    `addressdetail` varchar(255) default NULL,

    `addresses` int(11) default NULL,

    PRIMARY KEY  (`addressid`),

    KEY `FK9B93456DC08D1667` (`addresses`),

    CONSTRAINT `FK9B93456DC08D1667` FOREIGN KEY (`addresses`) REFERENCES `person_1nfk` (`personid`)

  ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=gbk;

 

  /* Formatted on 2007/08/21 10:07 (QP5 v5.50) */

  CREATE TABLE `person_1nfk` (

    `personid` int(11) NOT NULL auto_increment,

    `name` varchar(255) default NULL,

    `age` int(11) default NULL,

    PRIMARY KEY  (`personid`)

  ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gbk;

 

 

五、映射方法：在实体类Person里面添加Address的集合，即可形成一对多关系。

        <!--映射集合属性，关联到持久化类,inverse="false"表示主控端在Person1nfk端，lazy="false"表示不采用延迟加载-->

        <set name="addresses"

             table="ADDRESS_1nfk"

             cascade="all"

        >

            <!--确定关联的外键列-->

            <key column="personid"/>

            <!--用以映射到关联类属性-->

            <one-to-many class="com.lavasoft.dx._1_n_fk.Address1nfk"/>

        </set>

 

<hibernate-mapping>

    <class name="com.lavasoft.dx._1_n_fk.Person1nfk" table="PERSON_1nfk">

        <id name="personid">

            <generator class="identity"/>

        </id>

        <property name="name"/>

        <property name="age"/>

        <!--映射集合属性，关联到持久化类,inverse="false"表示主控端在Person1nfk端，lazy="false"表示不采用延迟加载-->

        <set name="addresses"

             table="ADDRESS_1nfk"

             cascade="all"

        >

            <!--确定关联的外键列-->

            <key column="personid"/>

            <!--用以映射到关联类属性-->

            <one-to-many class="com.lavasoft.dx._1_n_fk.Address1nfk"/>

        </set>

    </class>

</hibernate-mapping>

 

<hibernate-mapping>

    <class name="com.lavasoft.dx._1_n_fk.Address1nfk" table="ADDRESS_1nfk">

        <id name="addressid">

            <generator class="identity"/>

        </id>

        <property name="addressdetail"/>

    </class>

</hibernate-mapping>

 

 

六、测试方法

 

public class Test_1nfk {

    public static void main(String[] args){

        Address1nfk add1=new Address1nfk();

        Address1nfk add2=new Address1nfk();

        Person1nfk p=new Person1nfk();

 

        add1.setAddressdetail("郑州市经三路");

        add2.setAddressdetail("合肥市宿州路");

        p.setName("wang");

        p.setAge(30);

        p.getAddresses().add(add1);

        p.getAddresses().add(add2);

 

        Session session= HibernateUtil.getCurrentSession();

        Transaction tx=session.beginTransaction();

        session.save(add1);

        session.save(add2);

        session.save(p);

        tx.commit();

        HibernateUtil.closeSession();

    }

}

 

七、测试结果

 

1) :正常保存.

//        session.save(add1);

//        session.save(add2);

        session.save(p);

Hibernate: insert into PERSON_1nfk (name, age) values (?, ?)

Hibernate: insert into ADDRESS_1nfk (addressdetail) values (?)

Hibernate: insert into ADDRESS_1nfk (addressdetail) values (?)

Hibernate: update ADDRESS_1nfk set personid=? where addressid=?

Hibernate: update ADDRESS_1nfk set personid=? where addressid=?

 

2) :正常保存.

        session.save(add1);

        session.save(add2);

        session.save(p);

Hibernate: insert into ADDRESS_1nfk (addressdetail) values (?)

Hibernate: insert into ADDRESS_1nfk (addressdetail) values (?)

Hibernate: insert into PERSON_1nfk (name, age) values (?, ?)

Hibernate: update ADDRESS_1nfk set personid=? where addressid=?

Hibernate: update ADDRESS_1nfk set personid=? where addressid=?

 

3) :正常保存.

        session.save(add1);

        session.save(add2);

//        session.save(p);

Hibernate: insert into ADDRESS_1nfk (addressdetail) values (?)

Hibernate: insert into ADDRESS_1nfk (addressdetail) values (?)

 

 

 

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