From Gossip@caterpillar

Hibernate Gossip: 膥┯ - 睼家Α

硄盽匡ノ贺膥┯琈甮家Αぇ碞礚猭甅ノ贺家Α琘ㄇ薄猵眤临琌睼ノㄢ贺膥┯家Αㄒ睼ノ 膥 ┯ - Table per class hierarchy 籔 膥┯ - Table per  subclassノTable per class hierarchyよΑ盢 DefaultUser 琈甮T_USERτノTable per subclassよΑ盢PowerUser穝﹚竡妮┦琈甮T_Poweruser
    create table T_PowerUser (
        id bigint not null,
        otherProperty varchar(255),
        primary key (id)
    )

    create table T_USER (
        id bigint not null auto_increment,
        userType varchar(255) not null,
        name varchar(255),
        someProperty varchar(255),
        primary key (id)
    )

    alter table T_PowerUser
        add index id (id),
        add constraint id
        foreign key (id)
        references T_USER (id)

 眤ㄏノ<join>夹乓ㄓ﹚竡ㄒ
  • User.hbm.xml
<?xml version="1.0" encoding="utf-8"?> 
<!DOCTYPE hibernate-mapping 
 PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 
 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 

<hibernate-mapping package="onlyfun.caterpillar"> 

    <class name="User" table="T_USER"> 

        <id name="id" column="id"> 
            <generator class="native"/> 
        </id> 

        <discriminator column="userType"/> 
 
        <property name="name" column="name"/> 

        <subclass name="DefaultUser" 
                  discriminator-value="Default"> 
            <property name="someProperty" column="someProperty" /> 
        </subclass> 
 
        <subclass name="PowerUser" 
                  discriminator-value="Power"> 
           <join table="T_PowerUser">
		<key column="id" foreign-key="id"/>
                <property name="otherProperty" column="otherProperty"/>
           </join> 
        </subclass>  

    </class> 

</hibernate-mapping>

纗ンㄒ
Hibernate:
    insert
    into
        T_USER
        (name, userType)
    values
        (?, 'Power')
Hibernate:
    insert
    into
        T_PowerUser
        (otherProperty, id)
    values
        (?, ?)
Hibernate:
    insert
    into
        T_USER
        (name, someProperty, userType)
    values
        (?, ?, 'Default')

琩高ㄒ
Hibernate:
    select
        user0_.id as id0_,
        user0_.name as name0_,
        user0_.someProperty as someProp4_0_,
        user0_1_.otherProperty as otherPro2_1_,
        user0_.userType as userType0_
    from
        T_USER user0_
    left outer join
        T_PowerUser user0_1_
            on user0_.id=user0_1_.id

纗絛ㄒ
mysql> select * from t_user;
+----+----------+-------------+--------------+
| id | userType | name        | someProperty |
+----+----------+-------------+--------------+
|  1 | Power    | caterpillar | NULL         |
|  2 | Default  | Bush        | hu....hu...  |
+----+----------+-------------+--------------+
2 rows in set (0.00 sec)

mysql> select * from t_poweruser;
+----+---------------+
| id | otherProperty |
+----+---------------+
|  1 | Bla...Bla...  |
+----+---------------+
1 row in set (0.00 sec)

硂睼ノ家Α拜肈琌膥┯約outer join穦Θ拜肈眤<join>fetch妮┦select
        ...
            <join table="T_PowerUser" fetch="select">
                <key column="id" foreign-key="FK_USER"/>                 
                <property name="otherProperty" column="otherProperty"/>
            </join>
        ...

玥琩高ㄒㄓΩ琩高传ΘㄢΩselect琩高
Hibernate:
    select
        user0_.id as id0_,
        user0_.name as name0_,
        user0_.someProperty as someProp4_0_,
        user0_.userType as userType0_
    from
        T_USER user0_
Hibernate:
    select
        user_1_.otherProperty as otherPro2_1_
    from
        T_PowerUser user_1_
    where
        user_1_.id=?