（七）mybatis之多对一关系（复杂）

一、需求分析

需求：查询所有消费者信息，关联查询订单及商品信息，订单明细信息中关联查询查商品信息。
分析：一个消费者有多条订单，一条订单只有一个消费者但是有多条订单明细，一条订单明细只有一个商品信息。

二、建数据库和实体对象

Customer.java

package com.shyroke.entity;

import java.util.List;

public class Customer {
    private int id;
    private String name;
    private String sex;
    private String birthday;

//一个消费者有多条订单
    private List<Order> orderList;

//隐藏get和set方法
｝

Order.java

package com.shyroke.entity;

import java.util.List;

public class Order {
    private int orderId;
    private String Number;
    private String createTime;
    private String note;

    // 关联消费者信息，是一对一关系
    private Customer customer;

    // 关联订单明细信息，是一对多关系
    private List<OrderDesc> orderDescList;

//隐藏get和set方法

OrderDesc.java

package com.shyroke.entity;

import java.lang.annotation.Inherited;

public class OrderDesc {
    private int id;
    private String num;
    private String itemsId;
    private String ordersId;

    //关联商品信息，一对一关系
    private Items item;

//隐藏get和set方法

Items.java

package com.shyroke.entity;

public class Items {
    private int id;
    private String name;
    private String time;
//隐藏get和set方法
}

三、创建 CustomerMapper.java接口和 CustomerMapper.xml文件

CustomerMapper.java

package com.shyroke.mapper;

import java.util.List;

import com.shyroke.entity.Customer;

public interface CustomerMapper {
        public List<Customer> selectCustomAllInfo();
}

CustomerMapper.xml

<?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.shyroke.mapper.CustomerMapper">
    <resultMap type="com.shyroke.entity.Customer" id="customerMap">
        <id column="user_id" property="id" />
        <result column="user_name" property="name" />
        <result column="user_sex" property="sex" />
        <result column="user_birthday" property="birthday" />

<!-- Customer的成员属性orderList，即一个Customer消费者含有多个Order订单 -->
        <collection property="orderList" ofType="com.shyroke.entity.Order">
            <id column="order_id" property="orderId" />
            <result column="order_number" property="Number" />
            <result column="order_createTime" property="createTime" />
            <result column="order_note" property="note" />

<!-- Order的成员属性orderDescList，即一个Order订单含有多个OrderDesc订单明细 -->
            <collection property="orderDescList" ofType="com.shyroke.entity.OrderDesc">
                <id column="orders_desc_id" property="id" />
                <result column="orders_desc_num" property="num" />
                <result column="orders_desc_items_id" property="itemsId" />
                <result column="orders_desc_orders_id" property="ordersId" />

<!-- OrderDesc的成员属性item，即一个OrderDesc订单对应一个Items商品 -->
                <association property="item" javaType="com.shyroke.entity.Items">
                    <id column="item_id" property="id" />
                    <result column="item_name" property="name" />
                    <result column="item_time" property="time" />
                </association>
            </collection>
        </collection>
    </resultMap>
    
    <select id="selectCustomAllInfo" resultMap="customerMap">
        select
            customer.*,item.*,orders.*,ordersDesc.*
        from
            customer,item,orders,ordersDesc
        where
            orders.user_id=customer.user_id and ordersDesc.orders_desc_orders_id=orders.order_id
            and ordersDesc.orders_desc_items_id=item.item_id
    </select>

</mapper>

四、添加mapper到总配置文件

mybatis-config.xml：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/test?useUnicode=true&amp;useJDBCCompliantTimezoneShift=true&amp;useLegacyDatetimeCode=false&amp;serverTimezone=UTC" />
                <property name="username" value="root" />
                <property name="password" value="" />
            </dataSource>
        </environment>
    </environments>
    
    <mappers>
        <mapper class="com.shyroke.mapper.CustomerMapper"/>
    </mappers>
   
</configuration>

五、测试

package com.shyrolk.firstMybatis;

import java.awt.image.ImageProducer;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import javax.swing.plaf.synth.SynthSeparatorUI;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import com.shyroke.entity.Customer;
import com.shyroke.entity.Order;
import com.shyroke.mapper.CustomerMapper;

/**
 * Hello world!
 *
 */
public class App {
    public static void main(String[] args) throws IOException {
        String resource = "resource/mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        SqlSession session = sessionFactory.openSession();

        CustomerMapper customerMapper = session.getMapper(CustomerMapper.class);
        List<Customer> customersList = customerMapper.selectCustomAllInfo();

        System.out.println(customersList);

    }
}