mybatis的多对多映射

来源：互联网发布：java分布式集群框架编辑：程序博客网时间：2024/06/08 16:46

　本文来总结一下mybatis中的多对多映射，从第8节的文章中可以看出，用户表和商品表示多对多关系，它们两的多对多是通过订单项和订单明细这两张表所关联起来的，那么这一节主要来总结一下用户表和商品表之间的多对多映射。
　　首先在上一节的基础上继续写sql，

<code style="padding: 0px; border-radius: 0px; color: inherit; font-family: 'Source Code Pro', monospace;font-size:undefined; display: block; white-space: pre; word-wrap: normal; box-sizing: border-box;" class="language-sql hljs  has-numbering"><span style="box-sizing: border-box;" class="hljs-operator"><span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">SELECT</span>   orders.*,  <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">user</span>.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`username`</span>,  <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">user</span>.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`sex`</span>,  <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">user</span>.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`address`</span>,  orderdetail.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`id`</span> orderdetail_id,  orderdetail.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`items_id`</span>,  orderdetail.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`items_num`</span>,  orderdetail.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`orders_id`</span>,  items.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`name`</span> items_name,  items.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`detail`</span> items_detail,  items.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`price`</span> items_price<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">FROM</span>  orders,  <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">USER</span>,  orderdetail,  items<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">WHERE</span> orders.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`user_id`</span>=<span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">user</span>.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`id`</span> <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">AND</span> orders.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`id`</span> = orderdetail.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`orders_id`</span> <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">AND</span> orderdetail.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`items_id`</span>=items.<span class="hljs-string" style="color:#0880;box-sizing: border-box;">`id`</span></span></code><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li><li style="padding: 0px 5px; box-sizing: border-box;">9</li><li style="padding: 0px 5px; box-sizing: border-box;">10</li><li style="padding: 0px 5px; box-sizing: border-box;">11</li><li style="padding: 0px 5px; box-sizing: border-box;">12</li><li style="padding: 0px 5px; box-sizing: border-box;">13</li><li style="padding: 0px 5px; box-sizing: border-box;">14</li><li style="padding: 0px 5px; box-sizing: border-box;">15</li><li style="padding: 0px 5px; box-sizing: border-box;">16</li><li style="padding: 0px 5px; box-sizing: border-box;">17</li><li style="padding: 0px 5px; box-sizing: border-box;">18</li></ul><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li><li style="padding: 0px 5px; box-sizing: border-box;">9</li><li style="padding: 0px 5px; box-sizing: border-box;">10</li><li style="padding: 0px 5px; box-sizing: border-box;">11</li><li style="padding: 0px 5px; box-sizing: border-box;">12</li><li style="padding: 0px 5px; box-sizing: border-box;">13</li><li style="padding: 0px 5px; box-sizing: border-box;">14</li><li style="padding: 0px 5px; box-sizing: border-box;">15</li><li style="padding: 0px 5px; box-sizing: border-box;">16</li><li style="padding: 0px 5px; box-sizing: border-box;">17</li><li style="padding: 0px 5px; box-sizing: border-box;">18</li></ul>

　　因为多对多比较复杂，总公共有四张表，我们先来分析一下思路：

将用户信息映射到User中；
在User类中添加订单列表属性List<Orders>ordersList，将用户创建的订单映射到ordersList中；
在Orders中添加订单明细列表属性List<OrderDetail>orderDetails，将订单的明细映射到orderDetails中；
在OrderDetail中添加Items属性，将订单明细所对应的商品映射到Items中。

　　经过这样分析后，感觉虽然有点复杂，但是好像不是很难的样子，映射的方法也跟前面的一样，只不过这里表有点多，关系有点复杂。下面来写映射文件：

<code style="padding: 0px; border-radius: 0px; color: inherit; font-family: 'Source Code Pro', monospace;font-size:undefined; display: block; white-space: pre; word-wrap: normal; box-sizing: border-box;" class="language-xml hljs  has-numbering"><span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">select</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">id</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"findUserAndItemsResultMap"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">resultMap</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"UserAndItemsResultMap"</span>></span>    SELECT       orders.*,      user.`username`,      user.`sex`,      user.`address`,      orderdetail.`id` orderdetail_id,      orderdetail.`items_id`,      orderdetail.`items_num`,      orderdetail.`orders_id`,      items.`name` items_name,      items.`detail` items_detail,      items.`price` items_price    FROM      orders,      USER,      orderdetail,      items    WHERE orders.`user_id`=user.`id` AND orders.`id` = orderdetail.`orders_id` AND orderdetail.`items_id`=items.`id`<span class="hljs-tag" style="color:#06666;box-sizing: border-box;"></<span class="hljs-title" style="color:#0088;box-sizing: border-box;">select</span>></span></code><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li><li style="padding: 0px 5px; box-sizing: border-box;">9</li><li style="padding: 0px 5px; box-sizing: border-box;">10</li><li style="padding: 0px 5px; box-sizing: border-box;">11</li><li style="padding: 0px 5px; box-sizing: border-box;">12</li><li style="padding: 0px 5px; box-sizing: border-box;">13</li><li style="padding: 0px 5px; box-sizing: border-box;">14</li><li style="padding: 0px 5px; box-sizing: border-box;">15</li><li style="padding: 0px 5px; box-sizing: border-box;">16</li><li style="padding: 0px 5px; box-sizing: border-box;">17</li><li style="padding: 0px 5px; box-sizing: border-box;">18</li><li style="padding: 0px 5px; box-sizing: border-box;">19</li><li style="padding: 0px 5px; box-sizing: border-box;">20</li></ul><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li><li style="padding: 0px 5px; box-sizing: border-box;">9</li><li style="padding: 0px 5px; box-sizing: border-box;">10</li><li style="padding: 0px 5px; box-sizing: border-box;">11</li><li style="padding: 0px 5px; box-sizing: border-box;">12</li><li style="padding: 0px 5px; box-sizing: border-box;">13</li><li style="padding: 0px 5px; box-sizing: border-box;">14</li><li style="padding: 0px 5px; box-sizing: border-box;">15</li><li style="padding: 0px 5px; box-sizing: border-box;">16</li><li style="padding: 0px 5px; box-sizing: border-box;">17</li><li style="padding: 0px 5px; box-sizing: border-box;">18</li><li style="padding: 0px 5px; box-sizing: border-box;">19</li><li style="padding: 0px 5px; box-sizing: border-box;">20</li></ul>

　　接下来，写名为UserAndItemsResultMap的resultMap，由于主表查询的是User，所以在resultMap中的type应该写成User的完全限定名或者别名：

<code style="padding: 0px; border-radius: 0px; color: inherit; font-family: 'Source Code Pro', monospace;font-size:undefined; display: block; white-space: pre; word-wrap: normal; box-sizing: border-box;" class="language-xml hljs  has-numbering"><span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">resultMap</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">type</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"mybatis.po.User"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">id</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"UserAndItemsResultMap"</span>></span>    <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 用户信息 --></span>    <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">id</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"user_id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"id"</span>/></span>    <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"username"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"username"</span>/></span>    <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"sex"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"sex"</span>/></span>    <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"address"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"address"</span>/></span>    <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 订单信息 --></span>    <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 一个用户对应多个订单，使用collection --></span>    <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">collection</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"ordersList"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">ofType</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"mybatis.po.Orders"</span>></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">id</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"id"</span>/></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"user_id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"userId"</span>/></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"number"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"number"</span>/></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"createtime"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"createtime"</span>/></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"note"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"note"</span>/></span>        <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 订单明细信息 --></span>        <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 一个订单包括多个明细，使用collection --></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">collection</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"orderdetails"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">ofType</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"mybatis.po.Orderdetail"</span>></span>            <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">id</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"orderdetail_id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"id"</span>/></span>            <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items_id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"itemsId"</span>/></span>            <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items_num"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"itemsNum"</span>/></span>            <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"orders_id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"ordersId"</span>/></span>            <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 商品信息 --></span>            <span class="hljs-comment" style="color:#8800;box-sizing: border-box;"><!-- 一个明细对应一个商品信息，使用association --></span>            <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">association</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">javaType</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"mybatis.po.Items"</span>></span>                <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">id</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items_id"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"id"</span>/></span>                <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items_name"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"name"</span>/></span>                <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items_detail"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"detail"</span>/></span>                <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"><<span class="hljs-title" style="color:#0088;box-sizing: border-box;">result</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">column</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"items_price"</span> <span class="hljs-attribute" style="color:#66066;box-sizing: border-box;">property</span>=<span class="hljs-value" style="color:#0880;box-sizing: border-box;">"price"</span>/></span>            <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"></<span class="hljs-title" style="color:#0088;box-sizing: border-box;">association</span>></span>        <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"></<span class="hljs-title" style="color:#0088;box-sizing: border-box;">collection</span>></span>    <span class="hljs-tag" style="color:#06666;box-sizing: border-box;"></<span class="hljs-title" style="color:#0088;box-sizing: border-box;">collection</span>></span><span class="hljs-tag" style="color:#06666;box-sizing: border-box;"></<span class="hljs-title" style="color:#0088;box-sizing: border-box;">resultMap</span>></span></code><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li><li style="padding: 0px 5px; box-sizing: border-box;">9</li><li style="padding: 0px 5px; box-sizing: border-box;">10</li><li style="padding: 0px 5px; box-sizing: border-box;">11</li><li style="padding: 0px 5px; box-sizing: border-box;">12</li><li style="padding: 0px 5px; box-sizing: border-box;">13</li><li style="padding: 0px 5px; box-sizing: border-box;">14</li><li style="padding: 0px 5px; box-sizing: border-box;">15</li><li style="padding: 0px 5px; box-sizing: border-box;">16</li><li style="padding: 0px 5px; box-sizing: border-box;">17</li><li style="padding: 0px 5px; box-sizing: border-box;">18</li><li style="padding: 0px 5px; box-sizing: border-box;">19</li><li style="padding: 0px 5px; box-sizing: border-box;">20</li><li style="padding: 0px 5px; box-sizing: border-box;">21</li><li style="padding: 0px 5px; box-sizing: border-box;">22</li><li style="padding: 0px 5px; box-sizing: border-box;">23</li><li style="padding: 0px 5px; box-sizing: border-box;">24</li><li style="padding: 0px 5px; box-sizing: border-box;">25</li><li style="padding: 0px 5px; box-sizing: border-box;">26</li><li style="padding: 0px 5px; box-sizing: border-box;">27</li><li style="padding: 0px 5px; box-sizing: border-box;">28</li><li style="padding: 0px 5px; box-sizing: border-box;">29</li><li style="padding: 0px 5px; box-sizing: border-box;">30</li><li style="padding: 0px 5px; box-sizing: border-box;">31</li><li style="padding: 0px 5px; box-sizing: border-box;">32</li></ul><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li><li style="padding: 0px 5px; box-sizing: border-box;">9</li><li style="padding: 0px 5px; box-sizing: border-box;">10</li><li style="padding: 0px 5px; box-sizing: border-box;">11</li><li style="padding: 0px 5px; box-sizing: border-box;">12</li><li style="padding: 0px 5px; box-sizing: border-box;">13</li><li style="padding: 0px 5px; box-sizing: border-box;">14</li><li style="padding: 0px 5px; box-sizing: border-box;">15</li><li style="padding: 0px 5px; box-sizing: border-box;">16</li><li style="padding: 0px 5px; box-sizing: border-box;">17</li><li style="padding: 0px 5px; box-sizing: border-box;">18</li><li style="padding: 0px 5px; box-sizing: border-box;">19</li><li style="padding: 0px 5px; box-sizing: border-box;">20</li><li style="padding: 0px 5px; box-sizing: border-box;">21</li><li style="padding: 0px 5px; box-sizing: border-box;">22</li><li style="padding: 0px 5px; box-sizing: border-box;">23</li><li style="padding: 0px 5px; box-sizing: border-box;">24</li><li style="padding: 0px 5px; box-sizing: border-box;">25</li><li style="padding: 0px 5px; box-sizing: border-box;">26</li><li style="padding: 0px 5px; box-sizing: border-box;">27</li><li style="padding: 0px 5px; box-sizing: border-box;">28</li><li style="padding: 0px 5px; box-sizing: border-box;">29</li><li style="padding: 0px 5px; box-sizing: border-box;">30</li><li style="padding: 0px 5px; box-sizing: border-box;">31</li><li style="padding: 0px 5px; box-sizing: border-box;">32</li></ul>

　　是不是看起来有点复杂了，但是很有条理，一步步的深入即可，仔细看看，其实不是很复杂，就是有点多而已，一个个套进去呗~
　　下面就是写mapper接口了：

<code style="padding: 0px; border-radius: 0px; color: inherit; font-family: 'Source Code Pro', monospace;font-size:undefined; display: block; white-space: pre; word-wrap: normal; box-sizing: border-box;" class="language-java hljs  has-numbering"><span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">public</span> <span style="box-sizing: border-box;" class="hljs-class"><span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">interface</span> <span class="hljs-title" style="color:#66066;box-sizing: border-box;">UserMapperOrders</span> {</span>    <span class="hljs-comment" style="color:#8800;box-sizing: border-box;">//省去不相关代码</span>    <span class="hljs-comment" style="color:#8800;box-sizing: border-box;">//查询用户购买商品信息</span>    <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">public</span> List<User> <span style="box-sizing: border-box;" class="hljs-title">findUserAndItemsResultMap</span>() <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">throws</span> Exception;}</code><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li></ul><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li><li style="padding: 0px 5px; box-sizing: border-box;">8</li></ul>

　　测试一下：

<code style="padding: 0px; border-radius: 0px; color: inherit; font-family: 'Source Code Pro', monospace;font-size:undefined; display: block; white-space: pre; word-wrap: normal; box-sizing: border-box;" class="language-java hljs  has-numbering"><span class="hljs-annotation" style="color:#9b859d;box-sizing: border-box;">@Test</span><span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">void</span> <span style="box-sizing: border-box;" class="hljs-title">findUserAndItemsResultMap</span>() <span class="hljs-keyword" style="color:#0088;box-sizing: border-box;">throws</span> Exception {    SqlSession sqlSession = sqlSessionFactory.openSession();    UserMapperOrders userMapperOrders = sqlSession.getMapper(UserMapperOrders.class);    List<User> list = userMapperOrders.findUserAndItemsResultMap();    System.out.println(list);}</code><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li></ul><ul style="list-style: none; margin: 0px; padding: 6px 0px 40px; left: 0px; top: 0px; width: 50px; text-align: right; border-right-color: rgb(221, 221, 221); border-right-width: 1px; border-right-style: solid; position: absolute; box-sizing: border-box; background-color: rgb(238, 238, 238);" class="pre-numbering"><li style="padding: 0px 5px; box-sizing: border-box;">1</li><li style="padding: 0px 5px; box-sizing: border-box;">2</li><li style="padding: 0px 5px; box-sizing: border-box;">3</li><li style="padding: 0px 5px; box-sizing: border-box;">4</li><li style="padding: 0px 5px; box-sizing: border-box;">5</li><li style="padding: 0px 5px; box-sizing: border-box;">6</li><li style="padding: 0px 5px; box-sizing: border-box;">7</li></ul>

　　这样多对多的映射就搞定了。不过还有个问题，就是这里多对多的查询会把所有关联的表的信息都查询出来，然后放到pojo中的对应的List或者某个类中，所以即使我只查了个用户信息，但是这个用户里包含了订单，订单项，商品等信息，感觉装的有点多，好像有时候并不需要这么多冗余的数据出来，但是如果用resultType的话查询出来的字段必须对应pojo中的属性，如果有List等，需要手动装入才行。所以下面总结一下对于这种查询数据比较多的时候，resultType和resultMap各有什么作用？

比如我们只需要将查询用户购买的商品信息明细清单（如用户名、用户地址、购买商品名称、购买商品时间、购买商品数量），那么我们完全不需要其他的信息，这个时候就没必要使用resultMap将所有的信息都搞出来，我们可以自己定义一个pojo，包含我们需要的字段即可，然后查询语句只查询我们需要的字段，这样使用resultType会方便很多。
如果我们需要查询该用户的所有详细信息，比如用户点击该用户或者鼠标放上去，会出来跟该用户相关的订单啊，订单明细啊，商品啊之类的，然后我们要点进去看下详细情况的时候，那就需要使用resultMap了，必须将所有信息都装到这个User中，然后具体啥信息再从User中取，很好理解。
总结一点：使用resultMap是针对那些对查询结果映射有特殊要求的功能，，比如特殊要求映射成list中包括多个list。否则使用resultType比较直接。

　　到这里，mybatis的多对多映射就总结完了。

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