Hibernate 一对一外键单向关联

Hibernate 一对一外键单向关联

 

    事实上，单向1-1与N-1的实质是相同的，1-1是N-1的特例，单向1-1与N-1的映射配置也非常相似。只需要将原来的many-to-one元素增加unique="true"属性，用于表示N的一端也必须是唯一的，在N的一端增加了唯一的约束，即成为单向1-1。基于外键的单向1-1的配置将与无连接表N-1关联的many-to-one增加unique="true"属性即可。

 

一、模型介绍

 

一个人（Person）对应一个地址（Address）。

 

二、实体（省略getter、setter方法）

Person11fk实体类：

public class Person11fk {
    private int personid;
    private String name;
    private int age;
    private Address11fk address11fk;

 Address11fk实体类：

public class Address11fk {
    private int addressid;
    private String addressdetail;
 

 三、表模型

 

mysql> desc address_11fk;

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

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

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

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

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

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

 

mysql> desc person_11fk;

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

| 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  | UNI | NULL    |                |

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

 

四、生成的SQL脚本

CREATE TABLE `address_11fk` ( 
    `addressid` int(11) NOT NULL auto_increment, 
    `addressdetail` varchar(255) default NULL, 
    PRIMARY KEY    (`addressid`) 
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8; 
    
CREATE TABLE `person_11fk` ( 
    `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 `FK68A8818F3F45AA77` (`addressId`), 
    CONSTRAINT `FK68A8818F3F45AA77` FOREIGN KEY (`addressId`) REFERENCES `address_11fk` (`addressid`) 
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8; 

 五、映射方法：

 

    在Person中添加Address属性，映射配置为：

 <!--用来映射关联PO column是Address在该表中的外键列名,增加unique变成“1-1”-->
<many-to-one name="address11fk" column="addressId" unique="true"/>

 Address11fk实体的映射文件是：

<hibernate-mapping> 
        <class name="com.lavasoft.dx._1_1_fk.Address11fk" table="ADDRESS_11fk"> 
                <id name="addressid"> 
                        <generator class="identity"/> 
                </id> 
                <property name="addressdetail"/> 
        </class> 
</hibernate-mapping>

 Person11fk类的实体对应的映射文件是：

<hibernate-mapping> 
        <class name="com.lavasoft.dx._1_1_fk.Person11fk" table="PERSON_11fk"> 
                <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,增加unique变成“1-1”--> 
                <many-to-one name="address11fk" column="addressId" unique="true"/> 
        </class> 
</hibernate-mapping>

  

六、测试方法

public class Test_11fk { 
        public static void main(String[] args){ 
                Person11fk p1=new Person11fk(); 
    
                p1.setAge(21); 
                p1.setName("p1"); 
    
                Address11fk add1=new Address11fk(); 
                add1.setAddressdetail("郑州市经三路"); 
    
                p1.setAddress11fk(add1); 
    
                Session session= HibernateUtil.getCurrentSession(); 
                Transaction tx=session.beginTransaction(); 
                session.save(add1); 
                session.save(p1); 
                tx.commit(); 
                HibernateUtil.closeSession(); 
        } 
}

 七、测试结果

 

1) :正常保存. 推荐这么干!

session.save(add1);
session.save(p1);

 Hibernate: insert into ADDRESS_11fk (addressdetail) values (?)

Hibernate: insert into PERSON_11fk (name, age, addressId) values (?, ?, ?)

 

2) :正常保存.

session.save(p1);
session.save(add1);

 Hibernate: insert into PERSON_11fk (name, age, addressId) values (?, ?, ?)

Hibernate: insert into ADDRESS_11fk (addressdetail) values (?)

Hibernate: update PERSON_11fk set name=?, age=?, addressId=? where personid=?

 3) :正常保存.

//session.save(p1);
 session.save(add1);

 Hibernate: insert into ADDRESS_11fk (addressdetail) values (?)

4) : 发生异常,不能保存.

session.save(p1);
//session.save(add1);
 

 Hibernate: insert into PERSON_11fk (name, age, addressId) values (?, ?, ?)

Exception in thread "main" org.hibernate.TransientObjectException: com.lavasoft.dx._1_1_fk.Address11fk

 

from http://lavasoft.blog.51cto.com/62575/39279