Hibernate_映射_继承结构映射2_另外两种映射方式

<?xml version="1.0"?>

package cn.itcast.j_hbm_extends;

import java.util.Date;

/**
* 文章
*
* @author 风清杨
* @version V1.0
*/
public class Article {
private Integer id;
private String title;
private String content;
private Date postTime;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getTitle() {
return title;
}

public void setTitle(String title) {
this.title = title;
}

public String getContent() {
return content;
}

public void setContent(String content) {
this.content = content;
}

public Date getPostTime() {
return postTime;
}

public void setPostTime(Date postTime) {
this.postTime = postTime;
}

}
package cn.itcast.j_hbm_extends;

/**
* 主题
*
* @author 风清杨
* @version V1.0
*/
public class Topic extends Article {
private Integer type;// 精华、置顶...

public Integer getType() {
return type;
}

public void setType(Integer type) {
this.type = type;
}

}
package cn.itcast.j_hbm_extends;

/**
* 回贴
*
* @author 风清杨
* @version V1.0
*/
public class Reply extends Article {
private Integer floor;// 楼层

public Integer getFloor() {
return floor;
}

public void setFloor(Integer floor) {
this.floor = floor;
}

}
package cn.itcast.j_hbm_extends;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.Test;

/**
* 应用程序操作类
*
* @author 风清杨
* @version V1.0
*
*/
public class App {
private static SessionFactory sessionFactory = new Configuration()//
.configure()//
.addClass(Article.class)//
.buildSessionFactory();

// 保存,有关联关系
@Test
public void testSave() throws Exception {
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
// ------------------------------------

// 新键对象
Article article = new Article();
article.setTitle("这是一个Article");
Topic topic = new Topic();
topic.setTitle("这是一个Topic");
Reply reply = new Reply();
reply.setTitle("这是一个Reply");

// 保存
session.save(article);
session.save(topic);
session.save(reply);
// ------------------------------------
tx.commit();
} catch (RuntimeException e) {
tx.rollback();
throw e;
} finally {
session.close();
}
}

// 获取,可以获取到关联的对方
@Test
public void testGet() throws Exception {
Session session = sessionFactory.openSession();
Transaction tx = null;
try {
tx = session.beginTransaction();
// ------------------------------------
// 获取
Article article = (Article) session.get(Article.class, 1);
Topic topic = (Topic) session.get(Topic.class, 2);
Reply reply = (Reply) session.get(Reply.class, 3);

System.out.println(article);
System.out.println(topic);
System.out.println(reply);
System.out.println();

Article article1 = (Article) session.get(Article.class, 2);
Article article2 = (Article) session.get(Article.class, 3);
System.out.println(article1);
System.out.println(article2);
// ------------------------------------
tx.commit();
} catch (RuntimeException e) {
tx.rollback();
throw e;
} finally {
session.close();
}
}

}

方式1



<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 导入包 -->
<hibernate-mapping package="cn.itcast.j_hbm_extends2">
<!-- 采用每个类一张表的方式,抽象类也对应表 -->
<class name="Article" table="t_article">
<id name="id" type="integer" column="id_">
<generator class="native" />
</id>
<property name="title" type="string" column="title_" />
<property name="content" type="text" length="10000" column="content_"></property>
<property name="postTime" type="timestamp" column="postTime_"></property>

<!-- 子类：Topic -->
<joined-subclass name="Topic" table="t_topic">
<key column="articleId"></key>
<property name="type" type="integer" column="type_"/>
</joined-subclass>

<!-- 子类：Reply -->
<joined-subclass name="Reply" table="t_reply">
<key column="articleId"></key>
<property name="floor" type="integer" column="floor_"/>
</joined-subclass>
</class>
</hibernate-mapping>


方式2



<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 导入包 -->
<hibernate-mapping package="cn.itcast.j_hbm_extends3">
<!-- 采用每个具体类一张表的方式,抽象类不对应表
abstract默认为false,设为true表示本类不对应表(类可以不是abstract的),这时就会忽略table属性。
-->
<class name="Article" abstract="false">
<id name="id" type="integer" column="id_">

<!--
当使用每个具体类一张表的方式时,主键生成策略不能是identity。
因为在整个继承结构中,主键值是不能重复的。
-->
<generator class="hilo">
<param name="table">hi_value</param>
<param name="column">next_value</param>
<param name="max_lo">100</param>
</generator>
</id>
<property name="title" type="string" column="title_" />
<property name="content" type="text" length="10000" column="content_"></property>
<property name="postTime" type="timestamp" column="postTime_"></property>

<!-- 子类：Topic -->
<union-subclass name="Topic" table="t_topic">
<property name="type" type="integer" column="type_"/>
</union-subclass>

<!-- 子类：Reply -->
<union-subclass name="Reply" table="t_reply">
<property name="floor" type="integer" column="floor_"/>
</union-subclass>
</class>
</hibernate-mapping>