Mybatis-一对多

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/Category.xml"/>  
    </mappers>
</configuration>

3、Category

package com.llhc.model;

import java.util.List;

public class Category {
    private int id;
    private String name;
    List<Product> products;
    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 List<Product> getProducts() {
        return products;
    }
    public void setProducts(List<Product> products) {
        this.products = products;
    }
    @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;
    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、Category.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.llhc.model">
    <!-- 一 -->
        <resultMap type="Category" id="categoryBean">
            <id column="cid" property="id" />
            <result column="cname" property="name" />
     
            <!-- 一对多的关系 -->
            <!-- property: 指的是集合属性的值, ofType：指的是集合中元素的类型 -->
            <collection property="products" ofType="Product">
                <id column="pid" property="id" />
                <result column="pname" property="name" />
                <result column="price" property="price" />
            </collection>
        </resultMap>
     
        <!-- 关联查询分类和产品表 -->
        <select id="listCategory" resultMap="categoryBean">
            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<Category> cs = session.selectList("listCategory");
            for (Category c : cs) {
                System.out.println(c);
                List<Product> ps = c.getProducts();
                for (Product p : ps) {
                    System.out.println("\t"+p);
                }
            }
            session.commit();
            session.close();
        }
}