mybatis之一对多映射查询(十一)

需求:查询订单信息，关联查询订单明细信息及用户信息

分析需求

查询订单信息,关联查询用户信息,所以我们可以发现主信息为orders,从信息为user,orderdetail

sql语句

SELECT u.id uid, o.*, od.orders_id, od.items_id
FROM orders o
LEFT JOIN USER u
ON u.id = o.user_id
LEFT JOIN orderdetail od
ON o.id = od.orders_id
LEFT JOIN items i
ON i.id = od.items_id

修改扩展类

添加订单明细集合属性

package com.test.domain;

import java.util.List;

public class OrdersExt extends Orders {

private User user;

private List<Orderdetail> orderdetailList;

public List<Orderdetail> getOrderdetailList() {
return orderdetailList;
}
public void setOrderdetailList(List<Orderdetail> orderdetailList) {
this.orderdetailList = orderdetailList;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}

}

映射文件

extends属性为继承,值为resultMap 的id,在mybatis映射文件中也可以和java类一样可以继承

<?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.test.mapper.OrdersMapper">

<resultMap type="com.test.domain.OrdersExt" id="ordersAndUserResultMap">
<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"/>

<association property="user" javaType="com.test.domain.User">

4000
<id column="user_id" property="id"/>
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<result column="address" property="address"/>
</association>
</resultMap>

<resultMap type="com.test.domain.OrdersExt" id="ordersAndUserDetialResultMap" extends="ordersAndUserResultMap">
<collection property="orderdetailList" ofType="com.test.domain.Orderdetail">
<id property="id" column="od_id"/>
<result property="itemsId" column="items_id"/>
<result property="ordersId" column="orders_id"/>
<result property="itemsNum" column="items_num"/>
</collection>
</resultMap>
<select id="findOrdersAndUserAndOrderdetail" resultMap="ordersAndUserDetialResultMap">
SELECT u.username,
u.sex ,
u.address,
o.*,
od.id od_id,
od.orders_id,
od.items_id,
od.items_num
FROM orders o
LEFT JOIN USER u
ON u.id = o.user_id
LEFT JOIN orderdetail od
ON o.id = od.orders_id
</select>
</mapper>

OrdersMapper接口

package com.test.mapper;

import java.util.List;

import com.test.domain.OrdersExt;

public interface OrdersMapper {
List<OrdersExt> findOrdersAndUserAndOrderdetail();
}

测试代码

@Test
public void test_02(){
SqlSession sqlSession = sqlSessionFactory.openSession();

OrdersMapper mapper = sqlSession.getMapper(OrdersMapper.class);

List<OrdersExt> ordersExtList = mapper.findOrdersAndUserAndOrderdetail();

System.out.println(ordersExtList);
}