Hibernate_映射_继承结构映射1_使用一张表的方式

<?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_extends">
  <!-- 
    discriminator-value属性：
      用于鉴别是哪个类的一个值,表示这个值就是这个类。
      如果不写,默认为类的全限定名。
  -->
  <class name="Article" table="t_article" discriminator-value="Article">
    <id name="id" type="integer" column="id_">
      <generator class="native" />
    </id>
    <!-- 用于鉴别是什么类型的一个列 -->
    <discriminator type="string" column="class_"></discriminator>

    <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 -->
    <subclass name="Topic" discriminator-value="Topic">
      <property name="type" />
    </subclass>

    <!-- 子类：Reply -->
    <subclass name="Reply" discriminator-value="Reply">
      <property name="floor" />
    </subclass>
  </class>
</hibernate-mapping>

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();
    }
  }

}