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）

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

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=gbk;

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=gbk;

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"/>

<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>

<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