Hibernate 一對一連接表單向關聯

  這種情況很少見，但Hibernate同樣允許採用連接表關聯1-1.有連接表的1-1同樣只需要將N-1的many-to-one元素增加unique="true"屬性即可。

一、模型介紹

一個人（Person）對應一個地址（Address）。

二、實體（省略getter、setter方法）

public class Person11tab {

    private int personid;

    private String name;

    private int age;

    private Address11tab address11tab;

public class Address11tab {

    private int addressid;

    private String addressdetail;

三、表模型

mysql> desc address_11tab;

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

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

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

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

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

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

mysql> desc join_11tab;

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

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

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

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

| address11tab | int(11) | YES  | UNI | NULL    |       |

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

mysql> desc person_11tab;

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

| 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腳本

/* Formatted on 2007/08/20 16:52 (QP5 v5.50) */

CREATE TABLE `join_11tab` (

  `personid` int(11) NOT NULL,

  `address11tab` int(11) default NULL,

  PRIMARY KEY  (`personid`),

  UNIQUE KEY `address11tab` (`address11tab`),

  KEY `FK6B44BE20C4CC3D33` (`address11tab`),

  KEY `FK6B44BE209049BB1F` (`personid`),

  CONSTRAINT `FK6B44BE209049BB1F` FOREIGN KEY (`personid`) REFERENCES `person_11tab` (`personid`),

  CONSTRAINT `FK6B44BE20C4CC3D33` FOREIGN KEY (`address11tab`) REFERENCES `address_11tab` (`addressid`)

) ENGINE=InnoDB DEFAULT CHARSET=gbk;

/* Formatted on 2007/08/20 16:53 (QP5 v5.50) */

CREATE TABLE `address_11tab` (

  `addressid` int(11) NOT NULL auto_increment,

  `addressdetail` varchar(255) default NULL,

  PRIMARY KEY  (`addressid`)

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

/* Formatted on 2007/08/20 16:53 (QP5 v5.50) */

CREATE TABLE `person_11tab` (

  `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Person中添加Address屬性，映射配置爲：

        <!--使用join元素顯式確定鏈接表-->

        <join table="join_11tab">

            <key column="personid"/>

            <!--映射1-1關聯屬性，其中unique=“true”屬性確定爲“1-1”-->

            <many-to-one name="address11tab" unique="true"/>

        </join>

<hibernate-mapping>

    <class name="com.lavasoft.dx._1_1_tab.Person11tab" table="PERSON_11tab">

        <id name="personid">

            <generator class="identity"/>

        </id>

        <property name="name"/>

        <property name="age"/>

        <!--使用join元素顯式確定鏈接表-->

        <join table="join_11tab">

            <key column="personid"/>

            <!--映射1-1關聯屬性，其中unique=“true”屬性確定爲“1-1”-->

            <many-to-one name="address11tab" unique="true"/>

        </join>

    </class>

</hibernate-mapping>

<hibernate-mapping>

    <class name="com.lavasoft.dx._1_1_tab.Address11tab" table="ADDRESS_11tab">

        <id name="addressid">

            <generator class="identity"/>

        </id>

        <property name="addressdetail"/>

    </class>

</hibernate-mapping>

六、測試方法

public class Test_11tab {

    public static void main(String[] args){

        Person11tab p1=new Person11tab();

        p1.setAge(21);

        p1.setName("p1");

        Address11tab add1=new Address11tab();

        add1.setAddressdetail("鄭州市經三路");

        p1.setAddress11tab(add1);

        Session session= HibernateUtil.getCurrentSession();

        Transaction tx=session.beginTransaction();

        session.save(add1);

        session.save(p1);

        tx.commit();

        HibernateUtil.closeSession();

    }

}

七、測試結果

1) :正常保存. 推薦這麼幹!

        session.save(add1);

        session.save(p1);

Hibernate: insert into ADDRESS_11tab (addressdetail) values (?)

Hibernate: insert into PERSON_11tab (name, age) values (?, ?)

Hibernate: insert into join_11tab (address11tab, personid) values (?, ?)

2) :正常保存.

        session.save(p1);

        session.save(add1);

Hibernate: insert into PERSON_11tab (name, age) values (?, ?)

Hibernate: insert into join_11tab (address11tab, personid) values (?, ?)

Hibernate: insert into ADDRESS_11tab (addressdetail) values (?)

Hibernate: update join_11tab set address11tab=? where personid=?

3) :正常保存.

//        session.save(p1);

        session.save(add1);

Hibernate: insert into ADDRESS_11tab (addressdetail) values (?)

4) : 發生異常,不能保存.

        session.save(p1);

//        session.save(add1);

Hibernate: insert into PERSON_11tab (name, age) values (?, ?)

Hibernate: insert into join_11tab (address11tab, personid) values (?, ?)

Exception in thread "main" org.hibernate.TransientObjectException: com.lavasoft.dx._1_1_tab.Address11tab