Hibernate 一对一主键单向关联

1-1的关联可以基于主键关联，但基于主键关联的持久化类不能拥有自己的主键生成策略，它的主键由关联类负责生成。另外，另外，增加one-to-one元素来关联属性，必须为one-to-one元素增加constrained="true"属性，表明该类主键由关联类生成。
  
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 Person11pk {
    private int personid;
    private String name;
    private int age;
    private Address11pk address11pk;

public class Address11pk {
    private int addressid;
    private String addressdetail;

三、表模型

mysql> desc address_11pk;
+---------------+--------------+------+-----+---------+----------------+
| Field         | Type         | Null | Key | Default | Extra          |
+---------------+--------------+------+-----+---------+----------------+
| addressid     | int(11)      | NO   | PRI | NULL    | auto_increment |
| addressdetail | varchar(255) | YES  |     | NULL    |                |
+---------------+--------------+------+-----+---------+----------------+

mysql> desc person_11pk;
+----------+--------------+------+-----+---------+-------+
| Field    | Type         | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| personid | int(11)      | NO   | PRI |         |       |
| name     | varchar(255) | YES  |     | NULL    |       |
| age      | int(11)      | YES  |     | NULL    |       |
+----------+--------------+------+-----+---------+-------+

四、生成的SQL脚本

/* Formatted on 2007/08/22 14:40 (QP5 v5.50) */
CREATE TABLE `address_11pk` (
  `addressid` int(11) NOT NULL auto_increment,
  `addressdetail` varchar(255) default NULL,
  PRIMARY KEY  (`addressid`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=gbk;


/* Formatted on 2007/08/22 14:41 (QP5 v5.50) */
CREATE TABLE `person_11pk` (
  `presonid` int(11) NOT NULL,
  `name` varchar(255) default NULL,
  `age` int(11) default NULL,
  PRIMARY KEY  (`presonid`),
  KEY `FK68A882C591BB393E` (`presonid`),
  CONSTRAINT `FK68A882C591BB393E` FOREIGN KEY (`presonid`) REFERENCES `address_11pk` (`addressid`)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;


五、映射方法：在Person中配置id生成策略为：

        <id name="personid">
            <!--基于主键关联时，主键生成策略是foreign，表明根据关联类生成主键-->
            <generator class="foreign">
                <!--关联持久化类的属性名-->
                <param name="property">address11pk</param>
            </generator>
        </id>
        ......
        <!--用于映射1-1关联-->
        <one-to-one name="address11pk" constrained="true"/>

<hibernate-mapping>
    <class name="com.lavasoft.dx._1_1_pk.Person11pk" table="PERSON_11pk">
        <id name="personid" column="presonid">
            <!--基于主键关联时，主键生成策略是foreign，表明根据关联类生成主键-->
            <generator class="foreign">
                <!--关联持久化类的属性名-->
                <param name="property">address11pk</param>
            </generator>
        </id>
        <property name="name"/>
        <property name="age"/>
        <!--用于映射1-1关联-->
        <one-to-one name="address11pk" constrained="true"/>
    </class>
</hibernate-mapping>

<hibernate-mapping>
    <class name="com.lavasoft.dx._1_1_pk.Address11pk" table="ADDRESS_11pk">
        <id name="addressid">
            <generator class="identity"/>
        </id>
        <property name="addressdetail"/>
    </class>
</hibernate-mapping>


六、测试方法

public class Test_11pk {
    public static void main(String[] args){
        Person11pk p1=new Person11pk();

        p1.setAge(21);
        p1.setName("p1");

        Address11pk add1=new Address11pk();
        add1.setAddressdetail("郑州市经三路");

        p1.setAddress11pk(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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