Hibernate 关系配置（一对一，一对多）

关联关系：一对一　　一对一关系就球队与球队所在地之间的关系，一支球队仅有一个地址，而一个地区也仅有一支球队（貌似有点勉强，将就下吧）。数据表间一对一关系的表现有两种，一种是外键关联，一种是主键关联。图示如下：一对一外键关联：一对一主键关联：要求两个表的主键必须完全一致，通过两个表的主键建立关联关系：一对一外键关联在hbm文件中的配置信息：地址：

<?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">
<hibernate-mapping>
<class name="com.suxiaolei.hibernate.pojos.Adress" table="adress">
<id name="id" type="integer">
<column name="id"></column>
<generator class="increment"></generator>
</id>

<property name="city" column="city" type="string"></property>

<one-to-one name="team" class="com.suxiaolei.hibernate.pojos.Team" cascade="all"></one-to-one>

</class>
</hibernate-mapping>

球队：

<?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"><hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Team" table="team"><id name="id" type="integer"><column name="id"></column><generator class="increment"></generator></id><property name="name" column="name" type="string"></property><many-to-one name="adress" class="com.suxiaolei.hibernate.pojos.Adress" column="adress_id" unique="true"></many-to-one></class></hibernate-mapping>

一对一外键关联，其实可以看做是一对多的一种特殊形式，多方退化成一。多方退化成一只需要在<1954e;many-to-one>标签中设置"unique"="true"。一对一主键关联在hbm文件中的配置信息：地址：

<hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Adress" table="adress"><id name="id" type="integer"><column name="id"></column><generator class="increment"></generator></id><property name="city" column="city" type="string"></property><one-to-one name="team" class="com.suxiaolei.hibernate.pojos.Team" cascade="all"></one-to-one></class></hibernate-mapping>

球队：

<hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Team" table="team"><id name="id" type="integer"><column name="id"></column><generator class="foreign"><param name="property">adress</param></generator></id><property name="name" column="name" type="string"></property><one-to-one name="adress" class="com.suxiaolei.hibernate.pojos.Adress" cascade="all"></one-to-one></class></hibernate-mapping>

一对一主键关联，是让两张的主键值一样。要使两表的主键相同，只能一张表生成主键，另一张表参考主键。<generator class="foreign">　　<param name="property">adress</param></generator>"class"="foreign"就是设置team表的主键参照adress属性的主键值。关联关系：一对多（多对一）"一对多"是最普遍的映射关系，简单来讲就如消费者与订单的关系。一对多：从消费者角的度来说一个消费者可以有多个订单，即为一对多。多对一：从订单的角度来说多个订单可以对应一个消费者，即为多对一。 一对多关系在hbm文件中的配置信息：消费者（一方）：

<?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"><hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Customer" table="customer"><!-- 主键设置 --><id name="id" type="string"><column name="id"></column><generator class="uuid"></generator></id><!-- 属性设置 --><property name="username" column="username" type="string"></property><property name="balance" column="balance" type="integer"></property><set name="orders" inverse="true" cascade="all"><key column="customer_id" ></key><one-to-many class="com.suxiaolei.hibernate.pojos.Order"/></set></class></hibernate-mapping>

订单（多方）：

<?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"><hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Order" table="orders"><id name="id" type="string"><column name="id"></column><generator class="uuid"></generator></id><property name="orderNumber" column="orderNumber" type="string"></property><property name="cost" column="cost" type="integer"></property><many-to-one name="customer" class="com.suxiaolei.hibernate.pojos.Customer"column="customer_id" cascade="save-update"></many-to-one></class></hibernate-mapping>

　"一对多"关联关系，Customer方对应多个Order方，所以Customer包含一个集合用于存储多个Order，Order包含一个Customer用于储存关联自己的Customer。一对多关联关系有一种特例：自身一对多关联。例如：自身一对多关联自身的hbm文件设置：

<?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"><hibernate-mapping><class name="com.suxiaolei.hibernate.pojos.Category" table="category"><id name="id" type="string"><column name="id"></column><generator class="uuid"></generator></id><property name="name" column="name" type="string"></property><set name="chidrenCategories" cascade="all" inverse="true"><key column="category_id"></key><one-to-many class="com.suxiaolei.hibernate.pojos.Category"/></set><many-to-one name="parentCategory" class="com.suxiaolei.hibernate.pojos.Category" column="category_id"></many-to-one></class></hibernate-mapping>

外键存放父亲的主键。