Hibernate 一对一外键单向关联

    技术2022-05-19  25

    事实上,单向1-1N-1的实质是相同的,1-1N-1的特例,单向1-1N-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gettersetter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 columnAddress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  

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