MyBatis框架的多对多关联映射

今天药忘吃喽~ 2022-06-18 02:38 259阅读 0赞

代码：

Article.java

package com.bean;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class Article implements Serializable {
    	private Integer id;		// 商品id，主键
    	private String name;	// 商品名称
    	private Double price;	// 商品价格
    	private String remark;	// 商品描述
    	
    	// 商品和订单是多对多的关系，即一种商品可以包含在多个订单中
    	private List<Order> orders;
    
    	public Article() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	public Article(String name, Double price, String remark) {
    		super();
    		this.name = name;
    		this.price = price;
    		this.remark = remark;
    	}
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public Double getPrice() {
    		return price;
    	}
    
    	public void setPrice(Double price) {
    		this.price = price;
    	}
    
    	public String getRemark() {
    		return remark;
    	}
    
    	public void setRemark(String remark) {
    		this.remark = remark;
    	}
    
    	public List<Order> getOrders() {
    		return orders;
    	}
    
    	public void setOrders(List<Order> orders) {
    		this.orders = orders;
    	}
    
    	@Override
    	public String toString() {
    		// TODO Auto-generated method stub
    		return "Article [id=" + id + ", name=" + name + ", price=" + price + ", remark=" + remark + "]";
    	}
    }

Order.java

package com.bean;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class Order implements Serializable {
    	private Integer id;  // 订单id，主键
    	private String code;  // 订单编号
    	private Double total; // 订单总金额
    	
    	// 订单和用户是多对一的关系，即多个订单只属于一个用户
    	private User user;
    	
    	// 订单和商品是多对多的关系，即一个订单可以包含多种商品
    	private List<Article> articles;
    
    	public Order() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	public Order(String code, Double total) {
    		super();
    		this.code = code;
    		this.total = total;
    	}
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getCode() {
    		return code;
    	}
    
    	public void setCode(String code) {
    		this.code = code;
    	}
    
    	public Double getTotal() {
    		return total;
    	}
    
    	public void setTotal(Double total) {
    		this.total = total;
    	}
    
    	public User getUser() {
    		return user;
    	}
    
    	public void setUser(User user) {
    		this.user = user;
    	}
    
    	public List<Article> getArticles() {
    		return articles;
    	}
    
    	public void setArticles(List<Article> articles) {
    		this.articles = articles;
    	}
    
    	@Override
    	public String toString() {
    		// TODO Auto-generated method stub
    		return "Order [id=" + id + ", code=" + code + ", total=" + total + "]";
    	}
    	
    }

User.java

package com.bean;
    
    import java.io.Serializable;
    import java.util.List;
    
    public class User implements Serializable {
    	private Integer id;  // 用户id，主键
    	private String username;  // 用户名
    	private String loginname; // 登录名
    	private String password;  // 密码
    	private String phone;    // 联系电话
    	private String address;  // 收货地址
    	
    	// 用户和订单是一对多的关系，即一个用户可以有多个订单
    	private List<Order> orders;
    
    	public User() {
    		super();
    		// TODO Auto-generated constructor stub
    	}
    
    	public User(String username, String loginname, String password, String phone, String address) {
    		super();
    		this.username = username;
    		this.loginname = loginname;
    		this.password = password;
    		this.phone = phone;
    		this.address = address;
    	}
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getUsername() {
    		return username;
    	}
    
    	public void setUsername(String username) {
    		this.username = username;
    	}
    
    	public String getLoginname() {
    		return loginname;
    	}
    
    	public void setLoginname(String loginname) {
    		this.loginname = loginname;
    	}
    
    	public String getPassword() {
    		return password;
    	}
    
    	public void setPassword(String password) {
    		this.password = password;
    	}
    
    	public String getPhone() {
    		return phone;
    	}
    
    	public void setPhone(String phone) {
    		this.phone = phone;
    	}
    
    	public String getAddress() {
    		return address;
    	}
    
    	public void setAddress(String address) {
    		this.address = address;
    	}
    
    	public List<Order> getOrders() {
    		return orders;
    	}
    
    	public void setOrders(List<Order> orders) {
    		this.orders = orders;
    	}
    
    	@Override
    	public String toString() {
    		// TODO Auto-generated method stub
    		return "User [id=" + id + ", username=" + username + ", loginname="+ loginname + ", password=" + password + ", phone=" + phone + ", address=" + address + "]";
    	}
    	
    }

OrderMapper.java

package com.mapper;
    
    import com.bean.Order;
    
    public interface OrderMapper {
    	Order selectOrderById(int id);
    }

UserMapper.java

package com.mapper;
    
    import com.bean.User;
    
    public interface UserMapper {
    	User selectUserById(int id);
    }

ArticleMappr.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.mapper.ArticleMapper">
      <select id="selectArticleByOrderId" parameterType="int" resultType="com.bean.Article">
      	  SELECT * FROM tb_article WHERE id IN (SELECT article_id FROM tb_item WHERE order_id = #{id} ) 
      </select>
    </mapper>

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.mapper.OrderMapper">
    	<resultMap type="com.bean.Order" id="orderResultMap">
    		<id property="id" column="oid"/>
    	  	<result property="code" column="code"/>
    	  	<result property="total" column="total"/>
    		
    		<association property="user" javaType="com.bean.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" javaType="ArrayList"
    	     column="oid" ofType="com.bean.Article"
    	     select="com.mapper.ArticleMapper.selectArticleByOrderId" fetchType="lazy">
    	  	<id property="id" column="id"/>
    	  	<result property="name" column="name"/>
    	  	<result property="price" column="price"/>
    	  	<result property="remark" column="remark"/>
    	</collection>
     </resultMap>
    	
    	
      <select id="selectOrderById" parameterType="int" resultMap="orderResultMap">
      	 SELECT u.*,o.id AS oid,CODE,total,user_id FROM tb_user u,tb_order o
      	 WHERE u.id = o.user_id AND o.id = #{id}
      </select>
      
      
      <select id="selectOrderByUserId" parameterType="int" resultType="com.bean.Order">
      	  SELECT * FROM tb_order WHERE user_id = #{id}
      </select>
      
    
    </mapper>

UserMapper.xml

ManyToManyTest.java

package com.test;
    
    import java.io.InputStream;
    import java.util.List;
    
    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.bean.Article;
    import com.bean.Order;
    import com.bean.User;
    import com.mapper.OrderMapper;
    import com.mapper.UserMapper;
    
    public class ManyToManyTest {
    	// 测试一对多，查询班级User（一）的时候级联查询订单Order（多）  
    	public void testSelectUserById(SqlSession session){
    		// 获得UserMapper接口的代理对象
    		UserMapper um=session.getMapper(UserMapper.class);
    		// 调用selectUserById方法
    		User user = um.selectUserById(1);
    		// 查看查询到的user对象信息
    		System.out.println(user.getId() + " " + user.getUsername());
    		// 查看user对象关联的订单信息
    		List<Order> orders=user.getOrders();
    		for(Order order : orders){
    			System.out.println(order);
    		}
    	}
    	
    	// 测试多对多，查询订单Order（多）的时候级联查询订单的商品Article（多）  
    	public void testSelectOrderById(SqlSession session){
    		// 获得OrderMapper接口的代理对象
    		OrderMapper om = session.getMapper(OrderMapper.class);
    		// 调用selectOrderById方法
    		Order order = om.selectOrderById(2);
    		// 查看查询到的order对象信息
    		System.out.println(order.getId() + " " + order.getCode() + " " + order.getTotal());
    		// 查看order对象关联的用户信息
    		User user=order.getUser();
    		System.out.println(user);
    		// 查看order对象关联的商品信息
    		List<Article> articles = order.getArticles();
    		for(Article article : articles){
    			System.out.println(article);
    		}
    	}
    	
    	public static void main(String[] args) throws Exception {
    		// TODO Auto-generated method stub
    		// 读取mybatis-config.xml文件
    		InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
    		// 初始化mybatis，创建SqlSessionFactory类的实例
    	    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    		// 创建Session实例
    		SqlSession session = sqlSessionFactory.openSession();
    		ManyToManyTest test = new ManyToManyTest();
    		// 根据用户id查询用户，测试一对多
        	//test.testSelectUserById(session);
    		// 根据订单id查询订单，测试多对多
    		test.testSelectOrderById(session);
    		session.commit();
    		session.close();
    		
    	}
    
    }

截图：

![Center][]

根据订单id查询订单，测试多对多

![Center 1][]

根据用户id查询用户订单，测试一对多

[Center]: /images/20220618/d1f063d8659344fa8888d707d1f19bad.png
[Center 1]: /images/20220618/19f838cc27f942c693701533157e5aa8.png