mybaits中resultMap实现多对多查询映射

<!-- 多对多查询:一个用户创建多个订单，一个订单包含多个订单明细，一个订单明细包含一个商品 -->
<resultMap type="com.hbut.po.User" id="findUserItemsMap">
<!-- 一个用户 -->
<id column="usersId" property="id"/>
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<result column="address" property="address"/>

<!-- 多个订单 -->
<collection property="orderList" ofType="com.hbut.po.Orders">
<id column="id" property="id"/>
<result column="user_id" property="userId"/>
<result column="number" property="number"/>
<result column="createtime" property="createtime"/>
<result column="note" property="note"/>
<!-- 多个明细 -->
<collection property="orders" ofType="com.hbut.po.Orderdetail">
<id column="orderdetail_id" property="id"/>
<result column="orders_id" property="ordersId"/>
<result column="items_id" property="itemsId"/>
<result column="items_num" property="itemsNum"/>
<!--一个订单明细包含一个商品-->
<association property="items" javaType="com.hbut.po.Items">
<result column="name" property="name"/>
<result column="price" property="price"/>
<result column="detail" property="detail"/>
</association>
</collection>
</collection>

</resultMap>
<select id="findUserItems" resultMap="findUserItemsMap">
SELECT
orders.*,
`user`.id usersId,
USER.username,
USER.sex,
USER.address,
orderdetail.id orderdetail_id,
orderdetail.items_id,
orderdetail.items_num,
orderdetail.orders_id,
items.name,
items.price,
items.detail
FROM
orders,
USER,
orderdetail,
items
WHERE orders.user_id = user.id AND orderdetail.orders_id=orders.id AND orderdetail.items_id=items.id
</select>

User类:

//属性名和数据库表的字段对应

private int id;
private String username;// 用户姓名
private String sex;// 性别
private Date birthday;// 生日
private String address;// 地址

//一个用户可以创建多个订单
private List<Orders> orderList;

Orders类:

   private Integer id;

    private Integer userId;

    private String number;

    private Date createtime;

    private String note;

    //一个订单包含多个订单明细

    private List<Orderdetail> orders;

Orderdetail类

    private Integer id;

    private Integer ordersId;

    private Integer itemsId;

    private Integer itemsNum;

  //一个订单明细对应一个商品

    private Items items;

Items类（商品类）

    private Integer id;

    private String name;

    private Float price;

    private String pic;

    private Date createtime;

    private String detail;

运行结果:一个用户创建的多个订单，每个订单包含多个订单明细，每个订单明细包含一个商品