一对多关联（多对一）：
???一对多关联映射： ???????在多的一端添加一个外键指向一的一端，它维护的关系是一指向多 ???多对一关联映射： ???????咋多的一端加入一个外键指向一的一端，它维护的关系是多指向一
在配置文件中添加： ?? 在一一端使用<set><key></key><one-to-many></one-to-many></set> ?????? <key>指定的外键字段必须和<many-to-one>指定的外键字段一致 ? 在多一端使用<many-to-one>
数据库中customer表和order表的关系：
创建实体类：
public class Customer { ???private Integer id; ???private String name; ???private Character gender; ???private Integer age; ???private String level; ???//一对多 ???private Set<Order> orders = new HashSet<Order>(); ???????public Customer() { ???????super(); ???????????}
getters and setters｝public class Order { ???private Integer id; ???private String orderno; ???private String productName; ???????//多对一 ???private Customer customer; ???public Order() { ???????super(); ???????// TODO Auto-generated constructor stub ???}
getters and setters} 创建映射文件：
<hibernate-mapping> ???<class name="com.roxy.hibernate.pojo.Customer" table="t_customer"> ???????????<id name="id" column="c_id"> ???????????<generator class="native"></generator> ???????</id> ???????????????<property name="name" column="c_name" not-null="true"></property> ???????<property name="gender" column="c_gender" length="1"></property> ???????<property name="age" column="c_age"></property> ???????<property name="level" column="c_level" length="20"></property> ???????????????<set name="orders"> ???????????<key column="customer_id"></key> ???????????<one-to-many class="com.roxy.hibernate.pojo.Order"/> ???????</set> ???</class></hibernate-mapping>
<hibernate-mapping package="com.roxy.hibernate.pojo"> ???<!-- 类和表的映射 --> ???<class name="Order" table="t_order"> ???????<id name="id" column="id"> ???????????<generator class="native"></generator> ???????</id> ???????<!-- 其他属性映射 --> ???????<property name="orderno" column="orderno" length="20"></property> ???????<property name="productName" column="product_name" length="100"></property> ???????<!-- 多对一 --> ???????<many-to-one name="customer" class="Customer" column="customer_id" /> ???????</class></hibernate-mapping> ??
创建配置文件：
???????<!-- mapping文件 --> ???????<mapping resource="com/roxy/hibernate/pojo/Customer.hbm.xml"/> ???????<mapping resource="com/roxy/hibernate/pojo/Order.hbm.xml"/>
查看并分析SQL语句：
Hibernate: ???????alter table t_order ???????add constraint FKesy3n2gc3fa0s3trrk3tvyv9a ???????foreign key (customer_id) ???????references t_customer (c_id)
----- hibernate首先为t_order和t_customer添加外键关联
Hibernate: ????insert ????into ???????t_customer ???????(c_name, c_gender, c_age, c_level) ????values ???????(?, ?, ?, ?)
----- 向t_customer中插入数据（session.save(cust);）
Hibernate: ????insert ????into ???????t_order ???????(orderno, product_name, customer_id) ????values ???????(?, ?, ?)
----- 向t_order中插入数据（session.save(o1);）
Hibernate: ????insert ????into ???????t_order ???????(orderno, product_name, customer_id) ????values ???????(?, ?, ?)
----- 向t_order中插入数据（session.save(o2);）
Hibernate: ????update ???????t_order ????set ???????customer_id=? ????where ???????id=?
----- 维护两个表之间的关系，hibernate更新t_customer数据
Hibernate: ????update ???????t_order ????set ???????customer_id=? ????where ???????id=?
----- 维护两个表之间的关系，hibernate更新t_customer数据
Hibernate--一对多/多对一
原文地址：http://www.cnblogs.com/roxy/p/7608778.html