use how2java;
create table product_(
id int NOT NULL AUTO_INCREMENT,
name varchar(30)  DEFAULT NULL,
price float  DEFAULT 0,
cid int ,
PRIMARY KEY (id)
)AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

use how2java;
delete from category_;
INSERT INTO category_ VALUES (1,'category1');
INSERT INTO category_ VALUES (2,'category2');
delete from product_;
INSERT INTO product_ VALUES (1,'product a', 88.88, 1);
INSERT INTO product_ VALUES (2,'product b', 88.88, 1);
INSERT INTO product_ VALUES (3,'product c', 88.88, 1);
INSERT INTO product_ VALUES (4,'product x', 88.88, 2);
INSERT INTO product_ VALUES (5,'product y', 88.88, 2);
INSERT INTO product_ VALUES (6,'product z', 88.88, 2);

package com.how2java.pojo;

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 + "]";
	}

}

package com.how2java.pojo;

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 + "]";
	}
	
}

<?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.how2java.pojo">
		<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>

package com.how2java;
 
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.how2java.pojo.Category;
import com.how2java.pojo.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();
 
    }
}