北京北大青鸟通州校区学术部提供：
1 多对一
第一步 ：建立对象模型
User
-----------------------------
id：int
name：String
group：Group
Group
------------------------------
id:int
name:String
第二步：映射文件
XML代码
<?xml version="1.0"?>
<!DOCTYPE Hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="User" table="t_user">
<id name="id" column="id">
<generator class="identity"/>
</id>
<property name="name" column="User_name" unique="true"/>
<many-to-one name="group" column="groupid"/>
</class>
</hibernate-mapping>
2 一对一映射
2.1 主键映射
1. 建立对象模型
Person[id-int,name-String]
IdCard[id-int,cardNo-int]
2. 映射文件
Xml代码
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Person" table="t_person">
<id name="id">
<generator class="foreign">
<param name="property">idCard</param>
</generator>
</id>
<property name="name" column="Person_name" />
<one-to-one name="idCard" constrained="true"/>
</class>
</hibernate-mapping>
2.2 主键映射双向
只需要在IdCard 的XML中添加<one-to-one>标签指向person，就可以告诉Hibernate如何加载person，默认按照主键加载
2.3 外键关联映射
1. 对象模型
Person[id-int，name-String，idcard-IdCard]
IdCard[id-int，cardNo-int]
2 mapping文件
Xml代码
Person.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Person" table="t_person">
<id name="id">
<generator class="identity">
</generator>
</id>
<property name="name" column="Person_name" />
<many-to-one name="idCard" unique="true"></many-to-one>
</class>
</hibernate-mapping>
2.4 one-to-one 外键双向mapping
只需要在另一端（IdCard）加入<one-to-one>标签，但是hibernate默认按照主键加载，所以要告诉hibernate按照指定列来加载
示意：
Xml代码
Id-card
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="IdCard" table="t_idcard">
<id name="id" column="id">
<generator class="identity"/>
</id>
<property name="cardNo" column="cardno" />
<one-to-one name="person" property-ref
="idCard"></one-to-one>
</class>
</hibernate-mapping>
3 一对多映射
1 建立对象模型
Classes[id-int,name-String,student-Set]
Student[id-int,name-String]
2 映射文件
XML代码
<?xml version="1.0"?>
<!DOCTYPE Hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Class" table="t_class">
<id name="id">
<generator class="native"/>
</id>
<property name="name" />
<set name="student" >
<key column="classid" />
<one-to-many class="Student"/>
</set>
</class>
</hibernate-mapping>
缺点：若将Student的classid设置为非空，将无法保存。应为不是student这一端维护关系，所以student不知道是哪个班级，所以需要发出多余的update语句来更新关系。
4 多对多mapping
单向（采用第三方表）
1 对象模型
Role[id-int,name-String]
User[id-int,name-String,role-Set]
2映射文件
XML代码
<?xml version="1.0"?>
<!DOCTYPE Hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="User" table="t_user">
<id name="id">
<generator class="native"/>
</id>
<property name="name" />
<set name="role" table="t_user_role">
<key column="userid"></key>
<many-to-many class="Role" column="roleid" />
</set>
</class>
</hibernate-mapping>
双向：
1 对象模型：
Role[id-int,name-String,user-Set]
User[id-int,name-String,role-Set]
2 mapping文件：
Xml代码
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Role" table="t_role">
<id name="id">
<generator class="native"/>
</id>
<property name="name" />
<set name="user" table="t_user_role">
<key column="userid"></key>
<many-to-many class="User" column="userid" />
</set>
</class>
</hibernate-mapping>
5 继承mapping
第一类继承映射
1 对象模型
Animal
private int id
private String name
private Boolean sex
--------------------------------------------------
public class Bird extends Animal
private int height
--------------------------------------------------
public class Pig extends Animal
private int weight
2 mapping 文件
XML代码
<?xml version="1.0"?>
<!DOCTYPE Hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Animal" table="t_animal" >
<id name="id" >
<generator class="native"/>
</id>
<discriminator column="type" type="string"></discriminator>
<property name="name"/>
<property name="sex"/>
<subclass name="Pig" discriminator-value="P">
<property name="weight"/>
</subclass>
<subclass name="Bird" discriminator-value="B">
<property name="height"/>
</subclass>
</class>
</hibernate-mapping>
第二类mapping
1 对象模型
2 mapping 文件
XML代码
<?xml version="1.0"?>
<!DOCTYPE Hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Animal" table="t_animal" >
<id name="id" >
<generator class="native"/>
</id>
<property name="name"/>
<property name="sex"/>
<joined-subclass name="Pig" table="t_pig">
<key column="pid"/>
<property name="weight"/>
</joined-subclass>
<joined-subclass name="Bird" table="t_bird">
<key column="bid"/>
<property name="height"/>
</joined-subclass>
</class>
</hibernate-mapping>
3 第三类mapping
1对象模型
2 mapping 文件
Xml代码
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="Animal" table="t_animal" >
<id name="id" >
<generator class="native"/>
</id>
<property name="name"/>
<property name="sex"/>
<union-subclass name="Pig" table="t_pig">
<property name="weight"/>
</union-subclass>
<union-subclass name="Bird" table="t_bird">
<property name="height"/>
</union-subclass>
</class>
</hibernate-mapping>
6 Component 映射
component不是实体，没有OID。
1 对象模型
public class Employee
private int id
private String name
private Contact contact
-------------------------------------
public class Contact
private String email
private String address
private String zipcode
private String contactTel
-------------------------------------
public class User
private int id
private String name
private Contact contact
2 mapping文件
XML代码
<?xml version="1.0"?>
<!DOCTYPE Hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="User" table="t_user" >
<id name="id" >
<generator class="native"/>
</id>
<property name="name"/>
<component name="contact">
<property name="email"></property>
<property name="address"></property>
<property name="zipcode"></property>
<property name="contactTel"></property>
</component>
</class>
</hibernate-mapping>
7 复合主键mapping
通常将复合主键相关属性，单独放到一个类中
这个类必须实现 Serializable接口
这个类必须重写hashCode和equals方法
XML
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.nintenyun.hibernate">
<class name="SC" table="t_sc" >
<composite-id name="scpk">
<key-property name="sno"/>
<key-property name="cno"/>
</composite-id>
<property name="sname"></property>
<property name="cname"></property>
</class>
</hibernate-mapping>
