Mybatis-多对一

产品分类（多）产品（一）

代码

1、创建web应用，导入jar包
链接：https://pan.baidu.com/s/1uxLt_FUr2i2v7T7oGMUPLA 
提取码：nrji

数据库：
链接：https://pan.baidu.com/s/1mcosNNA5evb0liVQMXZlyA 
提取码：lzwq

2、src下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>
<!-- 扫描model -->
    <typeAliases>
      <package name="com.llhc.model"/>
    </typeAliases>
 <!-- 连接jdbc -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis1?characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
 <!-- 映射文件 -->
    <mappers>
        <mapper resource="com/llhc/model/Product.xml"/>
    </mappers>
</configuration>

3、Category

package com.llhc.model;

import java.util.List;

public class Category {
    private int id;
    private String name;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "Category [id=" + id + ", name=" + name + "]";
    }
     
}

4、Product

package com.llhc.model;

public class Product {
    private int id;
    private String name;
    private float price;
    private Category category;
    
    public Category getCategory() {
        return category;
    }
    public void setCategory(Category category) {
        this.category = category;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Product [id=" + id + ", name=" + name + ", price=" + price + "]";
    }
 
}

5、Product.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">
    <!-- 多对一 -->
    <mapper namespace="com.llhc.model">
    <!-- 多 -->
        <resultMap type="Product" id="productBean">
            <id column="pid" property="id" />
            <result column="pname" property="name" />
            <result column="price" property="price" />
     
     
            <!-- 多对一的关系 -->
            <!-- property: 指的是属性名称, javaType：指的是属性的类型 -->
            <association property="category" javaType="Category">
                <id column="cid" property="id"/>
                <result column="cname" property="name"/>
            </association>
        </resultMap>
        
     
        <!-- 根据id查询Product, 关联将Orders查询出来 -->
        <select id="listProduct" resultMap="productBean">
            select 
                c.*, p.*, c.id 'cid', p.id 'pid', c.name 'cname', p.name 'pname' 
            from 
                category_ c left join product_ p on c.id = p.cid
        </select>   
    </mapper>

6、TestMybatis

package com.llhc.controller;
import java.io.IOException;
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.llhc.model.Category;
import com.llhc.model.Product;
 
public class TestMybatis {
    public static void main(String[] args) throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
  
        List<Product> ps = session.selectList("listProduct");
        for (Product p : ps) {
            System.out.println(p+" 对应的分类是 \t "+ p.getCategory());
        }
 
        session.commit();
        session.close();
  
    }
}