hibernate关联配置

一、单向多对一

　　举例：多个订单对应一个顾客

　　顾客类Customer.java：

public class Customer{    private Integer customerId;    private String customerName;//get() set() 省略}

　　订单类Order.java：

public class Order {    private Integer orderId;    private String orderName;        private Customer customer;    /**    geter、seter   此处省略      **/}    

　　Customer.hbm.xml:

<class name="Customer" table="Customer">    <id name="customerId" column="COSTOMER_ID" type="integer">　　　　<generator class="native"/><!-- 主键生成策略native 不同数据库不同 -->　　</id>　　<property name="customerName" column="CUSTOMER_NAME" type="string"></property></class>

　　Order.hbm.xml:

<class name="Order" table="order">    <id name="orderId" column="ORDER_ID" type="integer">            <generator class="native"/>    </id>　　<property name="orderName" column="ORDER_NAME" type="string"></property>　　<!-- 映射多对一关系 -->　　<many-to-one name="customer" class="Customer" column="CUSTOMER_ID"></many-to-one></class>

二、双向多对一

　　顾客类 Customer.java:

public class Customer{    private Integer customerId;    private String customerName;//增加Set类型属性 并初始化空的Set    private Set<Order> orders = new HashSet<Order>();    //get() set() 省略}

　　订单类Order.java

public class Order {    private Integer orderId;    private String orderName;        private Customer customer;    /**    geter、seter   此处省略      **/}    

　　Customer.hbm.xml

<class name="Customer" table="Customer">    <id name="customerId" column="COSTOMER_ID" type="integer">　　　　<generator class="native"/>　　</id>　　<property name="customerName" column="CUSTOMER_NAME" type="string"></property>　　<set name="orders" table="order"  inverse="true"><!-- inverse设为true放弃维护关联关系 ， 又另一端单独维护 -->  　　  <key column="CUSTOMER_ID"></key><!-- 指定外键字段 -->　　　　<one-to-many class="Order"/>　　</set></class>

　　Order.hbm.xml

<class name="Order" table="order">    <id name="orderId" column="ORDER_ID" type="integer">            <generator class="native"/>    </id>　　<property name="orderName" column="ORDER_NAME" type="string"></property>　　<!-- 映射多对一关系 -->　　<many-to-one name="customer" class="Customer" column="CUSTOMER_ID"></many-to-one></class>

三、单向一对一

　　举例：一个部门Department 一个经理Manager

　　实体类：Department.java

public class Department{    private Integer departmentId;    private String departmentName;    private Manager manager;//省略geter seter;}

　　　Manager.java

public class Manager{    private Integer managerId;    private String managerName;//省略geter，seter；}

　　1)基于外键的单向一对一：Department.hbm.xml

<class name="Department" table="DEPARTMENTS" >        <id name="departmentId" column="DEPARTMENT_ID">            <generator class="native" />        </id>        <property name="departmentName" column="DEPARTMENT_NAME" type="string">        </property>        <!-- 使用many-to-one 映射一对一， 一对一是一种特殊的多对一 -->        <many-to-one name="manager" class="Manager" cascade="all" column="MANAGER_ID" unique="true"></many-to-one>    </class>

　　2）基于主键的单向1对1

<class name="Department" table="DEPARTMENTS" >        <id name="departmentId" column="DEPARTMENT_ID">            <generator class="foreign">                <param name="property">manager</param>            </generator>                    </id>        <property name="departmentName" column="DEPARTMENT_NAME" type="string">        </property>        <one-to-one name="manager" class="Manager" cascade="all" constrained="true"></one-to-one>    </class><!-- one-to-one的单向关联中，如果constrained=false，则会在查询时就全部取出来，用left outer join的方式。如果constrained=true，hibernate即会延迟加载sql，只把主表的查出来，等有用到关联表的再发sql取。 -->

 四、双向一对一

　　1）基于外键的双向一对一

　　Department.java:

public class Department{    private Integer departmentId;    private String departmentName;    private Manager Manager;}

　　Manager.java:

public class Manager{    private Integer managerId;    private String managerName;    private Department department;}

　　Department.hbm.xml:

<class name="Department" table="departments">  <id name="departmentId" column="DEPARTMENT_ID" type="integer">            <generator class="native" />  </id>  <property name="departmentName" column="DEPARTMENT_NAME" type="string">   </property>　　<many-to-one name="manager" column="MANAGER_ID" class="Manager" unique="true"/></class>

　　Manager.hbm.xml:

    <class name="Manager" table="MANAGERS">        <id name="managerId" column="MANAGER_ID" type="integer">            <generator class="native" />        </id>        <property name="managerName" column="MANAGER_NAME" type="string">        </property>        <!--  没有外键的一端，使用one-to-one进行映射，并指定property-ref属性为关联实体外键所对应的属性-->        <one-to-one name="department"  class="Department" property-ref="manager"></one-to-one>    </class>

　　2)基于主键的双向一对一：

　　Department.hbm.xml:

<class name="Department" table="departments">  <id name="departmentId" column="DEPARTMENT_ID" type="integer">            <generator class="foreign">　　　　　　　　<param name="property">manager</param> 　　　　　　</generator>  </id>  <property name="departmentName" column="DEPARTMENT_NAME" type="string">   </property>　<one-to-one name="manager" class="Manager" constrained="true"/></class>

　　Manager.hbm.xml:

<class name="Manager" table="MANAGERS">        <id name="managerId" column="MANAGER_ID" type="integer">            <generator class="native" />        </id>        <property name="managerName" column="MANAGER_NAME" type="string">        </property>        <one-to-one name="department" class="Department" ></one-to-one> </class>

五、单向多对多

多对多需要一个中间表

Category.java

public class Category {    private Integer id;    private String name;        private Set<Item> items = new HashSet<Item>();}

Item.java

public class Item {    private Integer id;    private String name;}

Category.hbm.xml

<class name="Category" table="CATEGORYS">        <id name="id" column="CATEGORY_ID" type="integer">            <generator class="native"></generator>        </id>        <property name="name" column="CATEGORY_NAME" type="string"></property>                <set cascade="all" name="items" table="CATEGORYS_ITEMS"><!--中间表的名字-->            <key column="CATEGORY_ID"></key>            <many-to-many class="Item" column="ITEM_ID"></many-to-many>                </set>    </class>

Item.hbm.xml

<class name="Item" table="ITEMS" >        <id name="id" column="ITEM_ID">            <generator class="native" />        </id>        <property name="name" column="ITEM_NAME" type="string">        </property>    </class>

六、双向多对多

Category.java

public class Category {    private Integer id;    private String name;        private Set<Item> items = new HashSet<Item>();}

Item.java

public class Item {    private Integer id;    private String name;    private Set<Category> categorys = new HashSet<Category>();}

Category.hbm.xml

<class name="Category" table="CATEGORYS">        <id name="id" column="CATEGORY_ID" type="integer">            <generator class="native"></generator>        </id>        <property name="name" column="CATEGORY_NAME" type="string"></property>                <set cascade="all" name="items" table="CATEGORYS_ITEMS"><!--中间表的名字-->            <key column="CATEGORY_ID"></key>            <many-to-many class="Item" column="ITEM_ID"></many-to-many>                </set>    </class>

Item.hbm.xml

<class name="Item" table="ITEMS" >        <id name="id" column="ITEM_ID">            <generator class="native" />        </id>        <property name="name" column="ITEM_NAME" type="string">        </property>                <set name="categorys" table="CATEGORYS_ITEMS" inverse="true"><!-- 必须有一端必须设置inverse -->            <key column="ITEM_ID"></key>            <many-to-many class="Category"  column="CATEGORY_ID"></many-to-many>        </set>    </class>

转载自：http://www.cnblogs.com/fanxiaofan/p/4321161.html