Hibernate继承映射--每个子类一个数据表的实现案例

这种方式，不再针对父类Container有专门的数据表和映射文件，hibernate隐性的通过
Container与两个子类的继承关系实现这一效果

数据库结构：

CREATE TABLE `box2` (
  `id` varchar(50) NOT NULL default '0',
  `size` double default NULL,
  `name` varchar(50) default NULL,
  `description` varchar(50) default NULL,
  `width` double default NULL,
  `height` double default NULL,
  `len` double default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gb2312;



CREATE TABLE `bottle2` (
  `id` varchar(50) NOT NULL default '0',
  `size` double default NULL,
  `name` varchar(20) default NULL,
  `diameter` double default NULL,
  `height` double default NULL,
  `description` varchar(50) default NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gb2312;

 实体关系：

 

package extendstesttwo;

public class Bottle extends Container ...{
  private double diameter;
  private double height;
public double getDiameter() ...{
    return diameter;
}
public void setDiameter(double diameter) ...{
    this.diameter = diameter;
}
public double getHeight() ...{
    return height;
}
public void setHeight(double height) ...{
    this.height = height;
}
}

package extendstesttwo;

public class Box extends Container ...{
    private double height;
    private double length;
    private double width;
    public double getHeight() ...{
        return height;
    }
    public void setHeight(double height) ...{
        this.height = height;
    }
    public double getLength() ...{
        return length;
    }
    public void setLength(double length) ...{
        this.length = length;
    }
    public double getWidth() ...{
        return width;
    }
    public void setWidth(double width) ...{
        this.width = width;
    }
}


package extendstesttwo;
//hibernate多态支持的策略，每个子类一张表
public abstract class Container ...{
  private String containerId;
  private double size;
  private String name;
  private String description;
public String getContainerId() ...{
    return containerId;
}
public void setContainerId(String containerId) ...{
    this.containerId = containerId;
}
public String getDescription() ...{
    return description;
}
public void setDescription(String description) ...{
    this.description = description;
}
public String getName() ...{
    return name;
}
public void setName(String name) ...{
    this.name = name;
}
public double getSize() ...{
    return size;
}
public void setSize(double size) ...{
    this.size = size;
}
}

映射文件：

<?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">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping package="extendstesttwo">
    <class name="Bottle" table="bottle2">
       <id name="containerId" column="id">
         <generator class="uuid.hex"></generator>
       </id>
       <property name="size" column="size"></property>
       <property name="name" column="name"></property>
       <property name="description" column="description"></property>
       <property name="height" column="height"></property>
       <property name="diameter" column="diameter"></property>
      </class>
</hibernate-mapping>

<?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">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping package="extendstesttwo">
    <class name="Box" table="box2">
       <id name="containerId" column="id">
         <generator class="uuid.hex"></generator>
       </id>
       <property name="size" column="size"></property>
       <property name="name" column="name"></property>
       <property name="description" column="description"></property>
       <property name="height" column="height"></property>
       <property name="width" column="width"></property>
       <property name="length" column="len"></property>
      </class>
</hibernate-mapping>

测试代码：
需要注意的是，由于没有Container的映射关系，此处需要用完成的包名
"from extendstesttwo.Container"

public static void main(String[] args) ...{
        Configuration cfg=new Configuration();
        cfg.configure();
        SessionFactory sf=cfg.buildSessionFactory();
        Session session=sf.openSession();
        Transaction t=session.beginTransaction();
        Box box1=new Box();
        box1.setName("木箱子");
        box1.setHeight(50);
        box1.setLength(50);
        box1.setWidth(50);
        box1.setDescription("包装电视机");
        box1.setSize(12500);
        
        Bottle bottle1=new Bottle();
        bottle1.setName("玻璃瓶子");
        bottle1.setDescription("喝牛奶用");
        bottle1.setSize(139.12);
        bottle1.setDiameter(6);
        bottle1.setHeight(12);
        
        session.save(box1);
        session.save(bottle1);
        
        
        //取全部Box
        Query query1=session.createQuery("from Box");
        for(Iterator iter=query1.list().iterator();iter.hasNext();)...{
            System.out.println(((Container)iter.next()).getName());
        }
       //取全部Bottle
        Query query2=session.createQuery("from Bottle");
        for(Iterator iter=query2.list().iterator();iter.hasNext();)...{
            System.out.println(((Container)iter.next()).getName());
        }
       //取全部container
        Query query3=session.createQuery("from extendstesttwo.Container");
        for(Iterator iter=query3.list().iterator();iter.hasNext();)...{
            System.out.println(((Container)iter.next()).getName());
        }
        t.commit();
        System.out.println("success");

    }

运行结果：
木箱子
Hibernate: select bottle0_.id as id0_, bottle0_.size as size0_, bottle0_.name as name0_, bottle0_.description as descript4_0_, bottle0_.height as height0_, bottle0_.diameter as diameter0_ from bottle2 bottle0_
玻璃瓶子
Hibernate: select box0_.id as id1_, box0_.size as size1_, box0_.name as name1_, box0_.description as descript4_1_, box0_.height as height1_, box0_.width as width1_, box0_.len as len1_ from box2 box0_
Hibernate: select bottle0_.id as id0_, bottle0_.size as size0_, bottle0_.name as name0_, bottle0_.description as descript4_0_, bottle0_.height as height0_, bottle0_.diameter as diameter0_ from bottle2 bottle0_
木箱子
玻璃瓶子
success

 

可以看到，这样也可以实现继承的查询

 

总结：目前继承查询有了三种方法了：<subselect>标签加上这两种继承（每个子类一个表，每个类一个表）策略（三种方式在我的blog的经验技巧之hibernate中都有相关文章，本文是第二种策略）