mybatis 一二事（3） - 多表关联查询

db.properties

 jdbc.driver=com.mysql.jdbc.Driver
 jdbc.url=jdbc:mysql://localhost:3306/order
 jdbc.username=root
 jdbc.password=root

SqlMapConfig.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>
     <!-- 加载数据库连接参数配置文件 -->
     <properties resource="db.properties" />

     <!--
         全局配置参数
         比如 二级缓存 延迟加载...等
         此全局参数会影响mybatis运行的性能，要谨慎配置
      -->
 <!--     <settings> -->
 <!--     <setting name="" value=""/> -->
 <!--     </settings> -->

     <!-- 定义别名 -->
     <typeAliases>
         <!-- 单个别名定义
         type：pojo的路径
         alias：别名的名称
         -->
         <!-- <typeAlias type="cn.itcast.mybatis.po.User" alias="user"/> -->
         <!-- 批量别名定义
         name：指定包名，将包下边的所有pojo定义别名 ，别名为类名（首字母大写或小写都行）
          -->
         <package name="com.mybatis.bean"/>
     </typeAliases>

     <!-- 和spring整合后 environments配置将废除 -->
     <environments default="development">
         <environment id="development">
             <transactionManager type="JDBC" />
             <dataSource type="POOLED">
                 <property name="driver" value="${jdbc.driver}"/>
                 <property name="url" value="${jdbc.url}"/>
                 <property name="username" value="${jdbc.username}"/>
                 <property name="password" value="${jdbc.password}"/>
             </dataSource>
         </environment>
     </environments>

     <!-- 配置mapper映射文件 -->
     <mappers>
         <!-- resource方式
         在UserMapper.xml，定义namespace为mapper接口的地址，映射文件通过namespace找到对应的mapper接口文件
          -->
         <!-- <mapper resource="sqlmap/UserMapper.xml" /> -->
         <!-- class方式
         class：指定 mapper接口的地址
         遵循规则：将mapper.xml和mapper.java文件放在一个目录 且文件名相同
          -->
         <!-- <mapper class="cn.itcast.mybatis.mapper.UserMapper"/> -->

         <!--
             批量mapper扫描
             遵循规则：将mapper.xml和mapper.java文件放在一个目录 且文件名相同
             主要以这样的方式为主来加载mapper
           -->
         <package name="com.mybatis.mapper"/>

     </mappers>
 </configuration>

OrderMapper.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.mybatis.mapper.OrderMapper" >

     <!--
         ********
         1 对 1 查询建议使用 resultType
         ********
      -->

     <!-- type 为主类，即A类包含了B类作为属性，则type就写A类 -->
     <resultMap type="Orders" id="orderUserResultMap">
         <!--
             id 和 result 这两个标签是映射到 Orders 中去的
             如果有多个字段决定id唯一，则写多个id标签
         -->
         <id column="id" property="id"/>
         <result column="order_number" property="order_number"/>
         <result column="user_id" property="user_id"/>

         <!--
             用于映射单个关联对象
             property: 将关联信息映射到哪个属性
             javaType: 属性映射的类型
          -->
         <association property="user" javaType="com.mybatis.bean.User">
             <id column="user_id" property="id"/>
             <result column="username" property="username"/>
             <result column="birthday" property="birthday"/>
         </association>
     </resultMap>    

     <!--
         extends： 继承上一个resultMap, 公用相同属性
      -->
     <resultMap type="Orders" id="orderUserDetailResultMap" extends="orderUserResultMap">

         <!--
             collection： 用于映射集合对象
             property: 将集合信息映射到哪个属性
             ofType: 这个集合对象的类型，也就是<>泛型
          -->
         <collection property="orderdetails" ofType="com.mybatis.bean.Orderdetail">
             <id column="order_detail_id" property="id"/>
             <result column="item_id" property="item_id"/>
             <result column="item_num" property="item_num"/>
             <result column="item_price" property="item_price"/>
         </collection>

     </resultMap>    

     <!--
         1 对 1 查询
      -->
     <select id="findOrderUserList" resultType="OrderUserCustom">
         select
             o.id,
             o.order_number,
             o.user_id,
             u.username,
             u.birthday
         from
             orders o
         inner join
             user u
         on
             o.user_id = u.id
     </select>

     <select id="findOrderUserListByResultMap" resultMap="orderUserResultMap">
         select
             o.id,
             o.order_number,
             o.user_id,
             u.username,
             u.birthday
         from
             orders o
         inner join
             user u
         on
             o.user_id = u.id
     </select>

     <!--
         1 对 多 查询
      -->
      <select id="findOrderItemsList" resultMap="orderUserDetailResultMap">
          select
                 o.id,
                 o.order_number,
                 o.user_id,
                 u.username,
                 u.birthday,
                 od.item_id,
                 od.item_num,
                 od.item_price,
                 od.id as order_detail_id
             from
                 orders o
             inner join
                 user u
             on
                 o.user_id = u.id
             left join
                 orderdetail od
             on
                 o.id = od.orders_id
     </select>
 </mapper>

OrderMapper.java

 package com.mybatis.mapper;

 import java.util.List;

 import com.mybatis.bean.OrderUserCustom;
 import com.mybatis.bean.Orders;

 public interface OrderMapper {

     public List<OrderUserCustom> findOrderUserList() throws Exception;

     public List<Orders> findOrderUserListByResultMap() throws Exception;

     public List<Orders> findOrderItemsList() throws Exception;

 }

Items.java

 package com.mybatis.bean;

 /**
  * 商品信息
  *
  * @author Thinkpad
  *
  */
 public class Items {
     private int id;// 商品id
     private String item_name;// 商品名称
     private Float item_price;// 商品价格
     private String item_detail;// 商品明细

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public String getItem_name() {
         return item_name;
     }

     public void setItem_name(String item_name) {
         this.item_name = item_name;
     }

     public Float getItem_price() {
         return item_price;
     }

     public void setItem_price(Float item_price) {
         this.item_price = item_price;
     }

     public String getItem_detail() {
         return item_detail;
     }

     public void setItem_detail(String item_detail) {
         this.item_detail = item_detail;
     }

 }

Orderdetail.java

 package com.mybatis.bean;

 /**
  * 订单明细
  *
  * @author Thinkpad
  *
  */
 public class Orderdetail {
     private int id;// 主键
     private int orders_id;// 订单id
     private int item_id;// 商品id
     private int item_num;// 商品数量
     private Float item_price;// 商品价格

     // 商品信息
     private Items items;// 明细对应的商品信息

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public int getOrders_id() {
         return orders_id;
     }

     public void setOrders_id(int orders_id) {
         this.orders_id = orders_id;
     }

     public int getItem_id() {
         return item_id;
     }

     public void setItem_id(int item_id) {
         this.item_id = item_id;
     }

     public int getItem_num() {
         return item_num;
     }

     public void setItem_num(int item_num) {
         this.item_num = item_num;
     }

     public Float getItem_price() {
         return item_price;
     }

     public void setItem_price(Float item_price) {
         this.item_price = item_price;
     }

     public Items getItems() {
         return items;
     }

     public void setItems(Items items) {
         this.items = items;
     }

 }

Orders.java

 package com.mybatis.bean;

 import java.util.List;

 /**
  * 订单信息
  *
  * @author Thinkpad
  *
  */
 public class Orders {
     private int id;// 订单id
     private int user_id;// 用户id
     private String order_number;// 订单号

     private User user;// 用户信息

     private List<Orderdetail> orderdetails;// 订单明细信息

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public int getUser_id() {
         return user_id;
     }

     public void setUser_id(int user_id) {
         this.user_id = user_id;
     }

     public String getOrder_number() {
         return order_number;
     }

     public void setOrder_number(String order_number) {
         this.order_number = order_number;
     }

     public User getUser() {
         return user;
     }

     public void setUser(User user) {
         this.user = user;
     }

     public List<Orderdetail> getOrderdetails() {
         return orderdetails;
     }

     public void setOrderdetails(List<Orderdetail> orderdetails) {
         this.orderdetails = orderdetails;
     }

 }

OrdersCustom.java

 package com.mybatis.bean;

 public class OrdersCustom extends User {

     private String user_id;// 用户id
     private String order_number;// 订单号

     public String getUser_id() {
         return user_id;
     }

     public void setUser_id(String user_id) {
         this.user_id = user_id;
     }

     public String getOrder_number() {
         return order_number;
     }

     public void setOrder_number(String order_number) {
         this.order_number = order_number;
     }

 }

OrderUserCustom.java

 package com.mybatis.bean;

 import java.util.Date;

 public class OrderUserCustom extends Orders {

     private String username;
     private Date birthday;
     public String getUsername() {
         return username;
     }
     public void setUsername(String username) {
         this.username = username;
     }
     public Date getBirthday() {
         return birthday;
     }
     public void setBirthday(Date birthday) {
         this.birthday = birthday;
     }

 }

User.java

 package com.mybatis.bean;

 import java.util.Date;
 import java.util.List;

 public class User implements java.io.Serializable {
     private int id;
     private int[] ids;// 存储多个id
     private String username;// 用户姓名
     private String sex;// 性别
     private Date birthday;// 出生日期
     private String address;// 地址
     private String detail;// 详细信息
     private Float score;// 成绩

     // 订单信息
     private List<Orders> orders;

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public String getUsername() {
         return username;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     public String getSex() {
         return sex;
     }

     public void setSex(String sex) {
         this.sex = sex;
     }

     public Date getBirthday() {
         return birthday;
     }

     public void setBirthday(Date birthday) {
         this.birthday = birthday;
     }

     public String getAddress() {
         return address;
     }

     public void setAddress(String address) {
         this.address = address;
     }

     public String getDetail() {
         return detail;
     }

     public void setDetail(String detail) {
         this.detail = detail;
     }

     public Float getScore() {
         return score;
     }

     public void setScore(Float score) {
         this.score = score;
     }

     @Override
     public String toString() {
         return "User [id=" + id + ", username=" + username + ", sex=" + sex
                 + ", birthday=" + birthday + ", address=" + address
                 + ", detail=" + detail + ", score=" + score + "]";
     }

     public List<Orders> getOrders() {
         return orders;
     }

     public void setOrders(List<Orders> orders) {
         this.orders = orders;
     }

     public int[] getIds() {
         return ids;
     }

     public void setIds(int[] ids) {
         this.ids = ids;
     }

 }

github地址：https://github.com/leechenxiang/mybatis003-order-reference-query