JavaSpring中級聯查詢

一對一級聯查詢映射文件PersonMapper.xml代碼：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper 
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace = "com.dao.PersonDao">

<!--方法1：嵌套查詢，執行兩個SQL語句-->
<resultMap type = "com.po.Person" id = "cardAndPerson1">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property = "card" column="idcard_id" javaType="com.po.Idcard"
select = "com.dao.IdCardDao.selectCodeById"/>
</resultMap>
<select id="selectPersonById1" parameterType="Integer" resultMap="cardAndPerson1">
 select * from person where id=#{id}
</select>


<!--方法2：嵌套查詢，執行一個SQL語句-->
<resultMap type = "com.po.Person" id="cardAndPerson2">
<id property = "id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="card" javaType="com.po.Idcard">
<id property = "id" column="idcard_id"/>
<result property = "code" column="code"/>
</association>
</resultMap>
<select id = "selectPersonById2" parameterType="Integer" resultMap="cardAndPerson2">
select p.*,ic.code
from person p,idcard ic
where p.idcard_id = ic.id and p.id=#{id}
</select>

<!--使用POJO存儲結果-->
<select id = "selectPersonById3" parameterType="Integer" resultType="com.pojo.SelectPersonById">
select p.*,ic.code
from person p,idcard ic
where p.idcard_id = ic.id and p.id=#{id}
</select>
</mapper>

IdCardMapper.xml代碼：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.dao.IdCardDao">
<select id="selectCodeById" parameterType="Integer" 
resultType="com.po.Idcard">
select * from idcard where id = #{id}
</select>
</mapper>

一對多查詢映射文件OrdersMapper.xml代碼：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.dao.OrdersDao">
<select id="selectOrdersById" parameterType="Integer" 
resultType="com.po.Orders">
select * from orders where user_id = #{id}
</select>
</mapper>

UserMapper.XML代碼：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空間應該是對應接口的包名+接口名 -->
<mapper namespace="com.dao.UserDao">
<!--id應該是接口中的方法，結果類型如沒有配置別名則應該使用全名稱 -->
<resultMap type="com.po.MyUser" id="userAndOrders1">
<id property="uid" column="uid"/>
<result property="uname" column="uname"/>
<result property="usex" column="usex"/>
<!--一對多級聯查詢，ofType表示集合中的元素類型，將uid傳遞給selectOrdersById-->
<collection property="ordersList" ofType="com.po.Orders" column="uid"
select ="com.dao.OrdersDao.selectOrdersById"/>
</resultMap>
<select id="selectUserOrdersById1" parameterType="Integer" 
resultMap="userAndOrders1">
select * from user where uid = #{id}
</select>

<resultMap type="com.po.MyUser" id="userAndOrders2">
<id property="uid" column="uid"/>
<result property="uname" column="uname"/>
<result property="usex" column="usex"/>
<collection property="ordersList" ofType="com.po.Orders">
<id property="id" column="id"/>
<result property="ordersn" column="ordersn"/>
</collection>
</resultMap>
<select id="selectUserOrdersById2" parameterType="Integer"
resultMap="userAndOrders2">
select u.*,o.id,o.ordersn
from user u,orders o
where u.uid = o.user_id and u.uid=#{id}
</select>
<--！使用POJO存儲結果-->
<select id="selectUserOrdersById3" parameterType="Integer"
resultType="com.pojo.SelectUserOrdersById">
select u.*,o.id,o.ordersn
from user u,orders o
where u.uid = o.user_id and u.uid=#{id}
</select>
</mapper>

多對多查詢，映射文件OrdersMapper.xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--命名空間應該是對應接口的包名+接口名 -->
<mapper namespace="com.dao.UserDao">
<!--id應該是接口中的方法，結果類型如沒有配置別名則應該使用全名稱 -->
<resultMap type="com.po.MyUser" id="userAndOrders1">
<id property="uid" column="uid"/>
<result property="uname" column="uname"/>
<result property="usex" column="usex"/>
<collection property="ordersList" ofType="com.po.Orders" column="uid"
select ="com.dao.OrdersDao.selectOrdersById"/>
</resultMap>
<select id="selectUserOrdersById1" parameterType="Integer" 
resultMap="userAndOrders1">
select * from user where uid = #{id}
</select>

<resultMap type="com.po.MyUser" id="userAndOrders2">
<id property="uid" column="uid"/>
<result property="uname" column="uname"/>
<result property="usex" column="usex"/>
<collection property="ordersList" ofType="com.po.Orders">
<id property="id" column="id"/>
<result property="ordersn" column="ordersn"/>
</collection>
</resultMap>
<select id="selectUserOrdersById2" parameterType="Integer"
resultMap="userAndOrders2">
select u.*,o.id,o.ordersn
from user u,orders o
where u.uid = o.user_id and u.uid=#{id}
</select>

<select id="selectUserOrdersById3" parameterType="Integer"
resultType="com.pojo.SelectUserOrdersById">
select u.*,o.id,o.ordersn
from user u,orders o
where u.uid = o.user_id and u.uid=#{id}
</select>
</mapper>