0051 MyBatis关联映射--多对多关系
用户与订单时一对多关系，再加上商品信息的话，订单与商品之间就是多对多关系了
DROP DATABASE IF EXISTS testdb;
USE testdb;
/*用户表，记录用户信息；用户与订单为一对多关系：一个用户可拥有多个订单*/
DROP TABLE IF EXISTS `tb_user`;
CREATE TABLE tb_user(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(18),
loginname VARCHAR(18),
PASSWORD VARCHAR(18),
phone VARCHAR(18),
address VARCHAR(18)
);
INSERT INTO tb_user(username,loginname,PASSWORD,phone,address) VALUES('杰克','jack','123456','13920001616','广州');
/*商品信息表；商品与订单为多对多关系：一个订单可有多个商品，一个商品也可出现在多个订单中*/
DROP TABLE IF EXISTS `tb_article`;
CREATE TABLE tb_article(
id INT PRIMARY KEY AUTO_INCREMENT,
NAME VARCHAR(32),
price DOUBLE,
remark VARCHAR(18)
);
INSERT INTO tb_article(NAME,price,remark) VALUES('疯狂Java讲义',108.9,'李刚老师经典着作');
INSERT INTO tb_article(NAME,price,remark) VALUES('疯狂Android讲义',99.9,'李刚老师经典着作');
INSERT INTO tb_article(NAME,price,remark) VALUES('疯狂iOS讲义',89.9,'李刚老师经典着作');
INSERT INTO tb_article(NAME,price,remark) VALUES('SpringMVC+MyBatis企业开发',69.9,'肖文吉老师经典着作');
/*订单表，记录订单编号，总金额，所属用户的id；订单与用户为多对一关系，与商品为多对多关系*/
DROP TABLE IF EXISTS `tb_order`;
CREATE TABLE tb_order(
id INT PRIMARY KEY AUTO_INCREMENT,
CODE VARCHAR(32),
total DOUBLE,
user_id INT,
FOREIGN KEY (user_id) REFERENCES tb_user(id)
);
INSERT INTO tb_order(CODE,total,user_id) VALUES('6aa3fa359ff14619b77fab5990940a2d',388.6,1);
INSERT INTO tb_order(CODE,total,user_id) VALUES('6aa3fa359ff14619b77fab5990940b3c',217.8,1);
/*中间表，用于记录订单对应的商品id*/
DROP TABLE IF EXISTS `tb_item`;
CREATE TABLE tb_item(
order_id INT,
article_id INT,
amount INT,
PRIMARY KEY(order_id,article_id),
FOREIGN KEY (order_id) REFERENCES tb_order(id),
FOREIGN KEY (article_id) REFERENCES tb_article(id)
);
INSERT INTO tb_item(order_id,article_id,amount) VALUES(1,1,1);
INSERT INTO tb_item(order_id,article_id,amount) VALUES(1,2,1);
INSERT INTO tb_item(order_id,article_id,amount) VALUES(1,3,2);
INSERT INTO tb_item(order_id,article_id,amount) VALUES(2,4,2);
INSERT INTO tb_item(order_id,article_id,amount) VALUES(2,1,1);
实体类User
package net.sonng.manytomany;
import java.util.List;
public class User {
private int id;
private String username;
private String loginname;
private String password;
private String phone;
private String address;
private List<Order> orders; //用户与订单：一对多关系，一个用户可有多个订单
//......
}
实体类Order
package net.sonng.manytomany;
import java.util.List;
public class Order {
private int id;
private String code;
private double total;
private int user_id;
private User user; //一个订单只属于一个用户
private List<Article> articles; //订单与商品：多对多关系，一个订单可包含多个商品，一个商品也可以出现在多个订单中
//.....
}
实体类Article
package net.sonng.manytomany;
import java.util.List;
public class Article {
private int id;
private String name;
private double price;
private String remark;
private List<Order> orders; //商品与订单：多对多关系
//.....
}
根据用户id查询用户信息，并将其所有订单信息一并查询出来
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTDMapper 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="net.sonng.manytomany.UserDao">
<select id="selectUserById" parameterType="int" resultMap="userMap">
SELECT * FROM tb_user WHERE id=#{user_id}
</select>
<resultMap id="userMap" type="net.sonng.manytomany.User">
<id property="id" column="id" />
<result property="username" column="username" />
<result property="loginname" column="loginname" />
<result property="password" column="password" />
<result property="phone" column="phone" />
<result property="address" column="address" />
<!-- 用户与订单一对多关系，用collection -->
<collection property="orders" column="id" javaType="ArrayList" ofType="net.sonng.manytomany.Order" select="net.sonng.manytomany.OrderDao.selectOrderByUserId" >
<id property="id" column="id" />
<result property="code" column="code" />
<result property="total" column="total" />
</collection>
</resultMap>
</mapper>
根据订单id查询订单信息，一并将其所属的用户信息和包含的商品信息查询出来
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTDMapper 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="net.sonng.manytomany.OrderDao">
<select id="selectOrderByUserId" parameterType="int" resultType="net.sonng.manytomany.Order" >
SELECT * FROM tb_order WHERE user_id=#{user_id}
</select>
<select id="selectOrderById" parameterType="int" resultMap="orderMap">
SELECT u.*,o.id AS oid,code,total,user_id FROM tb_order o,tb_user u WHERE o.user_id=u.id AND o.id=#{order_id}
</select>
<resultMap type="net.sonng.manytomany.Order" id="orderMap" >
<id property="id" column="id" />
<result property="code" column="code" />
<result property="total" column="total" />
<association property="user" javaType="net.sonng.manytomany.User">
<id property="id" column="id" />
<result property="username" column="username" />
<result property="loginname" column="loginname" />
<result property="password" column="password" />
<result property="phone" column="phone" />
<result property="address" column="address" />
</association>
<collection property="articles" column="id" javaType="ArrayList" ofType="net.sonng.manytomany.Article" select="net.sonng.manytomany.ArticleDao.selectArticleByOrderId" >
<id property="id" column="id" />
<result property="name" column="name" />
<result property="price" column="price" />
<result property="remark" column="remark" />
</collection>
</resultMap>
</mapper>
根据订单id，先从中间表item中查询其包含的商品id，再查询这些商品的信息
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//ibatis.apache.org//DTDMapper 3.0//EN" "http://ibatis.apache.org/dtd/ibatis-3-mapper.dtd">
<mapper namespace="net.sonng.manytomany.ArticleDao">
<select id="selectArticleByOrderId" parameterType="int" resultType="net.sonng.manytomany.Article">
SELECT * FROM tb_article WHERE id IN (SELECT article_id FROM tb_item WHERE order_id=#{order_id})
</select>
</mapper>
测试类
package net.sonng.test;
import java.util.List;
import net.sonng.manytomany.Article;
import net.sonng.manytomany.ArticleDao;
import net.sonng.manytomany.Order;
import net.sonng.manytomany.OrderDao;
import net.sonng.manytomany.User;
import net.sonng.manytomany.UserDao;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Test {
public static void main(String[] args){
ApplicationContext ac=new ClassPathXmlApplicationContext("ac.xml");
System.out.println("测试用户查询：根据用户id查询用户信息及其订单信息");
UserDao userDao=ac.getBean("userDao",UserDao.class);
User user=userDao.selectUserById(1);
System.out.println("------用户信息------");
System.out.println(user);
List<Order> orders=user.getOrders();
System.out.println("------该用户下的订单信息------");
for (Order order:orders){
System.out.println(order);
}
System.out.println("测试订单查询：根据订单id查询订单信息，所属用户信息，订单包含的商品信息");
OrderDao orderDao=ac.getBean("orderDao",OrderDao.class);
Order order=orderDao.selectOrderById(2);
System.out.println("------订单信息------");
System.out.println(order);
System.out.println("------订单所属用户信息------");
System.out.println(order.getUser());
List<Article> articles=order.getArticles();
System.out.println("------订单包含的商品信息------");
for (Article article:articles) {
System.out.println(article);
}
}
}
输出：
测试用户查询：根据用户id查询用户信息及其订单信息
------用户信息------
User [id=1, username=杰克, loginname=jack, password=123456, phone=13920001616, address=广州]
------该用户下的订单信息------
Order [id=1, code=6aa3fa359ff14619b77fab5990940a2d, total=388.6, user_id=1]
Order [id=2, code=6aa3fa359ff14619b77fab5990940b3c, total=217.8, user_id=1]
测试订单查询：根据订单id查询订单信息，所属用户信息，订单包含的商品信息
------订单信息------
Order [id=1, code=6aa3fa359ff14619b77fab5990940b3c, total=217.8, user_id=0]
------订单所属用户信息------
User [id=1, username=杰克, loginname=jack, password=123456, phone=13920001616, address=广州]
------订单包含的商品信息------
Article [id=1, name=疯狂Java讲义, price=108.9, remark=李刚老师经典着作]
Article [id=2, name=疯狂Android讲义, price=99.9, remark=李刚老师经典着作]
Article [id=3, name=疯狂iOS讲义, price=89.9, remark=李刚老师经典着作]
