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