1.多对一
product----category
我要评论category.hbm.xml
<?xml version="1.0"?>
<!doctype hibernate-mapping public
"-//hibernate/hibernate mapping dtd 3.0//en"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.h.pojo">
<class name="category" table="category_">
<id name="id" column="id">
<generator class="native">
</generator>
</id>
<property name="name" />
</class>
</hibernate-mapping>
product.hbm.xml
<?xml version='1.0' encoding='utf-8'?>
<!doctype hibernate-mapping public
"-//hibernate/hibernate mapping dtd 3.0//en"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.h.pojo">
<class name="product" table="product_">
<id name="id" column="id">
<generator class="native"></generator>
</id>
<property name="name" />
<property name="price" />
<many-to-one name="category" class="category" column="cid"></many-to-one> product多 对 一category
</class>
</hibernate-mapping>
hibernate.cfg.xml
<?xml version='1.0' encoding='utf-8'?>
<!doctype hibernate-configuration public
"-//hibernate/hibernate configuration dtd//en"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/test?characterencoding=utf-8</property>
<property name="connection.username">root</property>
<property name="connection.password">123456</property>
<!-- sql dialect -->
<property name="dialect">org.hibernate.dialect.mysqldialect</property>
<property name="current_session_context_class">thread</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>
<mapping resource="com/h/pojo/product.hbm.xml" />
<mapping resource="com/h/pojo/category.hbm.xml"/>
</session-factory>
</hibernate-configuration>
测试类：
public class test1 {
public static void main(string[] args) {
sessionfactory factory=new configuration().configure().buildsessionfactory();
session session = factory.opensession();
session.begintransaction();
category c =new category();
c.setname("c1");
session.save(c);
product p = (product) session.get(product.class, 2);
p.setcategory(c);
session.update(p);
session.gettransaction().commit();
session.close();
factory.close();
}
}
2.一对多
category 对 product，与多对一相反，就是一对多
测试类：
3.多对多
product ---- user
一种product可以被多个user购买
一个user可以购买多种product
所以product和user之间的关系是多对多 many-to-many
要实现多对多关系，必须有一张中间表 user_product 用于维护 user和product之间的关系
测试类：
数据库：
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