一．一对多的情况：
1.1------ 一对多中多的一方 有表又有类（双向，单向不另外做例，只需要去掉对应的<set>元素即可）
有一个B类，数据库有B类的对应表,B类多对一A类，那么就在A类中定义B对象的set集合，并在A的配置文件中使用
Customer.hbm.xml:
<hibernate-mapping>
<class name="mypack.Customer" table="CUSTOMERS">
<id name="id" type="long" column="ID">
<generator class="increment" />
</id>
<property name="name" type="string">
<column name="NAME" length="15" />
</property>
<set name="orders" inverse="true" cascade="save-update">
<key column="CUSTOMER_ID" />
<one-to-many class="mypack.Order" />
</set>
</class>
</hibernate-mapping>
Order.hbm.xml:
<hibernate-mapping >
<class name="mypack.Order" table="ORDERS">
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="orderNumber" type="string" >
<column name="ORDER_NUMBER" length="15" />
</property>
<many-to-one
name="customer"
column="CUSTOMER_ID"
class="mypack.Customer"
cascade="save-update"
/>
</class>
</hibernate-mapping>
1.2----- 一对多中多的一方 有表没有类
<!--[endif]-->
如果上面的描述变为B类并不存在，B类的属性全部作为一个值类型放到A中，但是数据库里面是有这个不存在的B类的表的，也就是跟上面的表一样，不一样的只是上面的B类的属性完全融入到了A中，那又该怎么表示呢？要如此表示：
<hibernate-mapping >
<class name="mypack.Customer" table="CUSTOMERS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="name" type="string" >
<column name="NAME" length="15" />
</property>
<property name="age" type="int" >
<column name="AGE" />
</property>
<set name="images" table="IMAGES" lazy="true" >
<key column="CUSTOMER_ID" />
<element column="FILENAME" type="string" not-null="true"/>
</set>
</class>
</hibernate-mapping>
---- 一对多中多的一方 有类没有表：
这个叫组成关系：比如
这种做如下配置：
<hibernate-mapping >
<class name="mypack.Customer" table="CUSTOMERS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="name" type="string" >
<column name="NAME" length="15" />
</property>
<component name="homeAddress" class="mypack.Address">
<parent name="customer" />
<property name="province" type="string" column="HOME_PROVINCE"/>
<property name="city" type="string" column="HOME_CITY"/>
<property name="street" type="string" column="HOME_STREET"/>
<property name="zipcode" type="string" column="HOME_ZIPCODE"/>
</component>
<component name="comAddress" class="mypack.Address">
<parent name="customer" />
<property name="province" type="string" column="COM_PROVINCE"/>
<property name="city" type="string" column="COM_CITY"/>
<property name="street" type="string" column="COM_STREET"/>
<property name="zipcode" type="string" column="COM_ZIPCODE"/>
</component>
</class>
</hibernate-mapping>
二．一对一的情况
2.1-------外键映射：
Address.hbm.xml:
<hibernate-mapping >
<class name="mypack.Address" table="ADDRESSES" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="city" column="CITY" type="string" />
<property name="province" column="PROVINCE" type="string" />
<property name="street" column="STREET" type="string" />
<property name="zipcode" column="ZIPCODE" type="string" />
<one-to-one name="customer"
class="mypack.Customer"
property-ref="homeAddress"
/>
</class>
</hibernate-mapping>
Customer.hbm.xml:
<hibernate-mapping >
<class name="mypack.Customer" table="CUSTOMERS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="name" column="NAME" type="string" />
<many-to-one name="homeAddress"
class="mypack.Address"
column="HOME_ADDRESS_ID"
cascade="all"
unique="true"
/>
<many-to-one name="comAddress"
class="mypack.Address"
column="COM_ADDRESS_ID"
cascade="all"
unique="true"
/>
<!-- unique的属性为true,表明每个Customer对象都有唯一的的homeAddress和comAdrress对象 -->
</class>
</hibernate-mapping>
2.2--------主键映射：
Address.hbm.xml:
<hibernate-mapping >
<class name="mypack.Address" table="ADDRESSES" >
<id name="id" type="long" column="ID">
<generator class="foreign">
<param name="property">customer</param>
</generator>
</id>
<property name="city" column="CITY" type="string" />
<property name="province" column="PROVINCE" type="string" />
<property name="street" column="STREET" type="string" />
<property name="zipcode" column="ZIPCODE" type="string" />
<one-to-one name="customer"
class="mypack.Customer"
constrained="true"
/>
<!--constrained 属性为true表明 ADDRESS 表的ID主键同时作为外键，参照CUSTOMERS表，同时必须还必须设置
<generator class="foreign">
<param name="property">customer</param>
</generator>
-->
</class>
</hibernate-mapping>
Customer.hbm.xml:
<hibernate-mapping >
<class name="mypack.Customer" table="CUSTOMERS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="name" column="NAME" type="string" />
<one-to-one name="address"
class="mypack.Address"
cascade="all"
/>
</class>
</hibernate-mapping>
三．多对多的情况（双向，单向的也不演示了）：
3.1--------没有加入组件集合的情况下：
Category.hbm.xml:
<hibernate-mapping>
<class name="mypack.Category" table="CATEGORIES">
<id name="id" type="long" column="ID">
<generator class="increment" />
</id>
<property name="name" column="NAME" type="string" />
<set name="items" table="CATEGORY_ITEM" lazy="true" cascade="save-update">
<key column="CATEGORY_ID" />
<many-to-many class="mypack.Item" column="ITEM_ID" />
</set>
</class>
</hibernate-mapping>
Item.hbm.xml:
<hibernate-mapping>
<class name="mypack.Item" table="ITEMS">
<id name="id" type="long" column="ID">
<generator class="increment" />
</id>
<property name="name" column="NAME" type="string" />
<property name="basePrice" column="BASE_PRICE" type="double" />
<set name="categories" table="CATEGORY_ITEM" lazy="true" inverse="true"
cascade="save-update">
<key column="ITEM_ID" />
<many-to-many class="mypack.Category" column="CATEGORY_ID" />
</set>
<!--在双向多对多关联的两端，必须把其中一段的<set>元素的inverse属性设置为“true”,且这一端只能使用<set>元素- -->
</class>
</hibernate-mapping>
3.2------------加入组件集合的情况下：
Order.hbm.xml:
<hibernate-mapping >
<class name="mypack.Order" table="ORDERS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="orderNumber" column="ORDER_NUMBER" type="string" />
<property name="price" formula=
"(select sum(line.BASE_PRICE*line.QUANTITY) from LINEITEMS line where line.ORDER_ID=ID)" />
<set name="lineItems" lazy="true" table="LINEITEMS" >
<key column="ORDER_ID" />
<composite-element class="mypack.LineItem" >
<parent name="order" />
<many-to-one name="item" class="mypack.Item" column="ITEM_ID" not-null="true"/>
<property name="quantity" column="QUANTITY" type="int" not-null="true" />
<property name="basePrice" column="BASE_PRICE" type="double" not-null="true" />
</composite-element>
</set>
<!----<composite-element> 用于映射lineItems组件类,为什么这么设计？因为到时候我们可以直接通过多态使用 order.getLineItem().add(linmeItem1)的
方法来加入组件类型。
---->
</class>
</hibernate-mapping>
Item.hbm.xml:
<hibernate-mapping >
<class name="mypack.Item" table="ITEMS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="name" column="NAME" type="string" />
<property name="basePrice" column="BASE_PRICE" type="double" />
<set name="lineItems" lazy="true" inverse="true" table="LINEITEMS" >
<key column="ITEM_ID" />
<composite-element class="mypack.LineItem" >
<parent name="item" />
<many-to-one name="order" class="mypack.Order" column="ORDER_ID" not-null="true"/>
<property name="quantity" column="QUANTITY" type="int" not-null="true" />
<property name="basePrice" column="BASE_PRICE" type="double" not-null="true" />
</composite-element>
</set>
</class>
</hibernate-mapping>
3.3--------将多对多的情况分解成两个一对多：
Item.hbm.xml:
<hibernate-mapping >
<class name="mypack.Item" table="ITEMS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="name" column="NAME" type="string" />
<property name="basePrice" column="BASE_PRICE" type="double" />
<set name="lineItems" lazy="true" inverse="true" cascade="save-update">
<key column="ITEM_ID" />
<one-to-many class="mypack.LineItem" />
</set>
</class>
</hibernate-mapping>
LineItem.hbm.xml:
<hibernate-mapping >
<class name="mypack.LineItem" table="LINEITEMS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="quantity" column="QUANTITY" type="int" />
<property name="basePrice" column="BASE_PRICE" type="double" />
<many-to-one name="order" column="ORDER_ID" class="mypack.Order" not-null="true" />
<many-to-one name="item" column="ITEM_ID" class="mypack.Item" not-null="true" />
</class>
</hibernate-mapping>
Order.hbm.xml:
<hibernate-mapping >
<class name="mypack.Order" table="ORDERS" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="orderNumber" column="ORDER_NUMBER" type="string" />
<set name="lineItems" lazy="true" inverse="true" cascade="save-update">
<key column="ORDER_ID" />
<one-to-many class="mypack.LineItem" />
</set>
</class>
</hibernate-mapping>
其实我觉得看那么多，眼都花了，最有用的还是一对多双向的情况，其他情况个人觉得实际应用并不多！折腾这么多干啥呀！
四．继承的情况（当然，肯定是类的继承，数据库的关系模型是不支持继承的）：
ClassA.hbm.xml:
<hibernate-mapping >
<class name="mypack.ClassA" table="TABLE_A" discriminator-value="A" >
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<discriminator column="A_TYPE" type="string" />
<property name="a1" type="string" column="A1" />
<subclass name="mypack.ClassC" discriminator-value="C" >
<property name="c1" column="C1" type="string" />
</subclass>
<subclass name="mypack.ClassD" discriminator-value="D" >
<property name="d1" column="D1" type="string" />
<subclass name="mypack.ClassG" discriminator-value="G" >
<property name="g1" column="G1" type="string" />
</subclass>
<subclass name="mypack.ClassH" discriminator-value="H" >
<property name="h1" column="H1" type="string" />
</subclass>
</subclass>
</class>
</hibernate-mapping>
ClassB.hbm.xml:
<hibernate-mapping >
<class name="mypack.ClassB" table="TABLE_B">
<id name="id" type="long" column="ID">
<generator class="increment"/>
</id>
<property name="b1" type="string" column="B1" />
<joined-subclass name="mypack.ClassE" table="TABLE_E">
<key column="B_ID" />
<property name="e1" column="E1" type="string" />
<property name="e2" column="E2" type="string" />
<property name="e3" column="E3" type="string" />
<property name="e4" column="E4" type="string" />
<property name="e5" column="E5" type="string" />
<property name="e6" column="E6" type="string" />
</joined-subclass >
<joined-subclass name="mypack.ClassF" table="TABLE_F">
<key column="B_ID" />
<property name="f1" column="F1" type="string" />
<property name="f2" column="F2" type="string" />
<property name="f3" column="F3" type="string" />
<property name="f4" column="F4" type="string" />
<property name="f5" column="F5" type="string" />
<property name="f6" column="F6" type="string" />
</joined-subclass >
</class>
</hibernate-mapping>