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hibernate繼承-joined-subclass 已更新(五)

還是和前面一樣。。先看先看由滿江紅翻譯團隊(RedSaga Translate Team)翻譯的配置說明

每個子類可能被映射到他自己的表中(每個子類一個表的策略)。被繼承的狀態通過和超類的表關聯得到。我們使用<joined-subclass>元素。

<joined-subclass
        name="ClassName"                    (1)
        table="tablename"                   (2)
        proxy="ProxyInterface"              (3)
        lazy="true|false"                   (4)
        dynamic-update="true|false"
        dynamic-insert="true|false"
        schema="schema"
        catalog="catalog"
        extends="SuperclassName"
        persister="ClassName"
        subselect="SQL expression"
        entity-name="EntityName"
        node="element-name">

        <key .... >

        <property .... />
        .....
</joined-subclass>

(1)	`name`: 子類的全限定名。
(2)	`table`: 子類的表名.
(3)	`proxy` (可選): 指定一個類或者接口，在延遲裝載時作為代理使用。
(4)	`lazy` (可選, 默認是 `true`): 設置為 `lazy="false"` 禁止使用延遲裝載。

這種映射策略不需要指定辨別標志(discriminator)字段。但是，每一個子類都必須使用<key>元素指定一個表字段來持有對象的標識符。

好了。。。開始寫代碼了。。。
1.建表

create?table?animal

(aid?varchar(32)?not?null?primary?key)

create?table?dog

(aid?varchar(32)?not?null?primary?key,

?dname?varchar(16)

)

create?table?cat

(aid?varchar(32)?not?null?primary?key,

?cname?varchar(16)

)

?2 寫vo
?2.1 Animal.java

package?com.test;

public?class?Animal

{

????private?String?aid;

??//getter?setter

2.2
Car.java

package?com.test;

public?class?Cat?extends?Animal

{

????private?String?cname;

//寫上?get?set?方法

? 2.3
Dog.java

package?com.test;

public?class?Dog?extends?Animal

{

????private?String?dname;

//寫getter?setter

3.寫配置文件

<?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>

????????

????????<joined-subclass?name="com.test.Dog"?table="dog">

????????????<key?column="aid"/>

????????????<property?name="dname">

????????????????<column?name="dname"?sql-type="varchar(16)"/>

????????????</property>

????????</joined-subclass>

????????<joined-subclass?name="com.test.Cat"?table="cat">

????????????<key?column="aid"/>

????????????<property?name="cname">

????????????????<column?name="cname"?sql-type="varchar(16)"/>

????????????</property>

????????</joined-subclass>

????</class>

</hibernate-mapping>

4.寫上測試類

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?TestInherit2

{

????SessionFactory?sf;

????Session?session;

????public?TestInherit2()

????{

????????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)

????{

????????TestInherit2?t?=?new?TestInherit2();

????????//t.doCreate();

????????t.doQuery();

????}

}

posted on 2006-04-11 22:28 record java and net 閱讀(3415) 評論(1) 編輯收藏所屬分類: java


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# re: hibernate繼承-joined-subclass 已更新(五) 2011-12-02 11:30 陳小東

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