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;
`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 >
< 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 >
< 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();
}
}
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
本文转自 leizhimin 51CTO博客，原文链接：http://blog.51cto.com/lavasoft/39279，如需转载请自行联系原作者
