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<subclass
        name="ClassName"                              (1)
        discriminator-value="discriminator_value"     (2)
        proxy="ProxyInterface"                        (3)
        lazy="true|false"                             (4)
        dynamic-update="true|false"
        dynamic-insert="true|false"
        entity-name="EntityName"
        node="element-name">
        <property .... />
        .....
</subclass>

每個子類都應該定義它自己的持久化屬性和子類。 <version> 和<id> 屬性可以從根父類繼承下來。在一棵繼承樹上的每個子類都必須定義一個唯一的discriminator-value。如果沒有指定，就會使用Java類的全限定名。

可以在單獨的映射文件中，直接在hibernate-mapping下定義subclass，union-subclass和joined-subclass映射。這樣你只要增加一個新的映射文件就可以繼承一棵類繼承樹。你必須在子類的映射中指定extends 屬性來指定已映射的超類。注意：以前，這個特性使得映射文件的順序變得很重要。從Hibernate3開始，當使用extends關鍵字的時候，映射文件的次序便不重要了。而在單一映射文件中，依舊需要保持將超類定義在子類之前這樣的次序。

<hibernate-mapping>
    <subclass name="DomesticCat" extends="Cat" discriminator-value="D">
         <property name="name" type="string"/>
    </subclass>
</hibernate-mapping>

create?table?animal
(aid?varchar(32)?not?null?primary?key,
?atype?varchar(16),
?dname?varchar(16),
?cname?varchar(16)
)

package?com.test;

public?class?Animal
{
????private?String?aid;
???//geter?seter

package?com.test;

public?class?Cat?extends?Animal
{
????private?String?cname;
??//geter?seter

package?com.test;

public?class?Dog?extends?Animal
{
????private?String?dname;
???//geter?seter

<?xml?version="1.0"?>
<!DOCTYPE?hibernate-mapping
????PUBLIC?"-//Hibernate/Hibernate?Mapping?DTD//EN"
????"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

????<class?name="com.test.Animal"?table="animal">??

????????<id?name="aid"?type="string"?unsaved-value="null"?>
????????????<column?name="aid"?sql-type="char(32)"?not-null="true"/>
????????????<generator?class="uuid.hex"/>
????????</id>

????????<discriminator?column="atype"?type="string"?/>
????????
????????<subclass?name="com.test.Dog"?discriminator-value="dog">
????????????<property?name="dname">
????????????????<column?name="dname"?sql-type="varchar(16)"?/>
????????????</property>
????????</subclass>

????????<subclass?name="com.test.Cat"?discriminator-value="cat">
????????????<property?name="cname">
????????????????<column?name="cname"?sql-type="varchar(16)"/>
????????????</property>
????????</subclass>

????</class>

</hibernate-mapping>

package?com.test;

import?net.sf.hibernate.Session;
import?net.sf.hibernate.SessionFactory;
import?net.sf.hibernate.cfg.Configuration;
import?net.sf.hibernate.*;
import?java.sql.*;
import?java.util.List;
import?java.util.Iterator;

public?class?TestInherit
{
????SessionFactory?sf;
????Session?session;
????public?TestInherit()
????{
????????try
????????{
????????????Configuration?cfg?=?new?Configuration();
????????????sf?=?cfg.addClass(Animal.class).buildSessionFactory();
????????}
????????catch(HibernateException?ex)
????????{
????????????ex.printStackTrace();
????????}
????}
????//插入
????public?void?doCreate()
????{
????????try
????????{
????????????session?=?sf.openSession();

????????????Dog?dog?=?new?Dog();
????????????dog.setDname("small?dog");
????????????Cat?cat?=?new?Cat();
????????????cat.setCname("small?cat");
????????????session.save(dog);
????????????session.save(cat);
????????????session.flush();
????????????session.connection().commit();

????????}
????????catch(HibernateException?ex)
????????{
????????????ex.printStackTrace();
????????}
????????catch(SQLException?ex1)
????????{
????????????ex1.printStackTrace();
????????}
????????finally
????????{
????????????????try{
????????????????????session.close();
????????????????}
????????????????catch(HibernateException?ex2){
????????????????}
????????}

????}
????//查詢
????public?void?doQuery()
????{
????????try{
????????????session?=?sf.openSession();
????????????Query?q?=?session.createQuery("select?d?from?Dog?as?d");
????????????List?l?=?q.list();
????????????Dog?dog?=?null;
????????????Cat?cat?=?null;
????????????for(int?i=0;i<l.size();i++)
????????????{
????????????????dog?=?(Dog)l.get(i);
????????????????System.out.println(dog.getDname());
????????????}
????????}
????????catch(HibernateException?ex){
????????????ex.printStackTrace();
????????}
????????finally{
????????????try{
????????????????session.close();
????????????}
????????????catch(HibernateException?ex2){
????????????}
????????}
????}
????public?static?void?main(String[]?args)
????{
????????TestInherit?t?=?new?TestInherit();
????????//t.doCreate();
????????t.doQuery();
????}
}