配置继承结构

来源：互联网发布：2016年8月淘宝消保新规编辑：程序博客网时间：2024/06/09 21:28

配置映射结构由三种方式：

1.整个继承结构使用一张表 <subclass...>

<?xml version="1.0" encoding="gbk"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><!--   This mapping demonstrates      (1) a table-per-subclass mapping strategy              (2) a simple component mapping          (3) recursive associations withing an inheritance tree     --><hibernate-mapping package="demoextends"><class name="Article" table="t_article" discriminator-value="Article"><id name="id" ><generator class="native"> <!--表示自动增长--></generator></id><!--用于鉴别是什么哪个类的列   鉴别值--><discriminator type="string" column="class_"></discriminator>        <property name="title" type="string" /><property name="content" type="text" length="10000"  /><property name="posttime" type="timestamp"  /><subclass name="Topic" discriminator-value="Topic"><property name="type"> </property></subclass><subclass name="Reply" discriminator-value="Reply"><property name="floor" > </property></subclass></class></hibernate-mapping>

2.每个类对应一张表，抽象类也对应表，每个表中只有当前类的属性。<joined-subclass....>

<?xml version="1.0" encoding="gbk"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><!--   This mapping demonstrates      (1) a table-per-subclass mapping strategy              (2) a simple component mapping          (3) recursive associations withing an inheritance tree     --><hibernate-mapping package="extends2"><class name="Article" table="t_article" ><!--采用每个类对应一张表的方式--><id name="id" ><generator class="native"> <!--表示自动增长--></generator></id>        <property name="title" type="string" /><property name="content" type="text" length="10000"  /><property name="posttime" type="timestamp"  /><joined-subclass name="Topic" table="t_topic"><key column="id"></key><property name="type"> </property></joined-subclass><joined-subclass name="Reply" table="t_reply"><key column="id"></key><property name="floor" > </property></joined-subclass></class></hibernate-mapping>

3.每个具体类对应一张表，抽象类不对应表，每个类中都有全部的信息，包括继承过来的信息。<union-subclass..>

<?xml version="1.0" encoding="gbk"?><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><!--   This mapping demonstrates      (1) a table-per-subclass mapping strategy              (2) a simple component mapping          (3) recursive associations withing an inheritance tree     --><hibernate-mapping package="extends3"><!--采用每个具体类对应一张表的方式，抽象类不对应表。abstract默认为false，设为true，表示不对应表。会忽略table属性--><class name="Article"  abstract="true"><id name="id" ><!--采用每个具体类对应一张表的方式，不能设置主键生成侧率为native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" /><property name="content" type="text" length="10000"  /><property name="posttime" type="timestamp"  /><union-subclass name="Topic" table="t_topic3"><property name="type"> </property></union-subclass><union-subclass name="Reply" table="t_reply3"><property name="floor" > </property></union-subclass></class></hibernate-mapping>

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