MyBatis解决字段名与实体类属性名不相同的冲突（四）

CREATE TABLE orders(
    order_id INT PRIMARY KEY AUTO_INCREMENT,
    order_no VARCHAR(20), 
    order_price FLOAT
);
INSERT INTO orders(order_no, order_price) VALUES('a1', 23);
INSERT INTO orders(order_no, order_price) VALUES('a2', 33);
INSERT INTO orders(order_no, order_price) VALUES('a3', 22);

package codeRose.dao;

public class Order {
    //实体类的中属性名与表中字段名不一致
    private int id;
    private String orderNO;
    private float price;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getOrderNO() {
        return orderNO;
    }
    public void setOrderNO(String orderNO) {
        this.orderNO = orderNO;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    @Override
    public String toString() {
        return "Order [>;
    }
    
    

}

<?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="codeRose.mapping.ordeMapper">
<!-- 
        根据id查询得到一个order对象，使用这个查询是查询不到我们想要的结果的，
        这主要是因为实体类的属性名和数据库的字段名对应不上的原因，因此无法查询出对应的记录
     -->
    <select id="getOrderById" parameterType="int" 
        resultType="codeRose.dao.Order">
        select * from orders where order_id=#{id}
    </select>
    
    <!-- 
        根据id查询得到一个order对象，使用这个查询是可以正常查询到我们想要的结果的，
        这是因为我们将查询的字段名都起一个和实体类属性名相同的别名，这样实体类的属性名和查询结果中的字段名就可以一一对应上
     -->
    <select id="selectOrder" parameterType="int" 
        resultType="codeRose.dao.Order">
        select order_id id, order_no orderNo,order_price price from orders where order_id=#{id}
    </select>
    
    <!-- 
    根据id查询得到一个order对象，使用这个查询是可以正常查询到我们想要的结果的，
    这是因为我们通过<resultMap>映射实体类属性名和表的字段名一一对应关系 -->
    <select id="selectOrderResultMap" parameterType="int" resultMap="orderResultMap">
        select * from orders where order_id=#{id}
    </select>
    <!--通过<resultMap>映射实体类属性名和表的字段名对应关系 -->
    <resultMap type="codeRose.dao.Order" id="orderResultMap">
        <!-- 用id属性来映射主键字段 -->
        <id property="id" column="order_id"/>
        <!-- 用result属性来映射非主键字段 -->
        <result property="orderNo" column="order_no"/>
        <result property="price" column="order_price"/>
    </resultMap>
</mapper>

<!-- 注册sql映射文件 -->
<mappers>
<!-- 包名/文件名 -->
<mapper resource="codeRose/mapping/userMapper.xml"/>
<mapper resource="codeRose/mapping/orderMapper.xml"/>

</mappers>

import org.apache.ibatis.session.SqlSession;

import codeRose.dao.Order;
import codeRose.util.MyBatisUtil;

public class Test2 {
    
    
    public void testById(){
        
        SqlSession sqlSession=MyBatisUtil.getSqlSession();
        //映射sql标识的字符串
        String statement="codeRose.mapping.orderMapper.getOrderById";
        Order order=sqlSession.selectOne(statement,1);
        sqlSession.close();
        System.out.println(order);//
    
    }
    public void testSelectOrder(){
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        String statement="codeRose.mapping.orderMapper.selectOrder";
        Order order =sqlSession.selectOne(statement, 1);
        sqlSession.close();
        System.out.println(order);
        
    }
    public void testSelectOrder2(){
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        String statement ="codeRose.mapping.orderMapper.orderResultMap";
        Order order =sqlSession.selectOne(statement, 1);
        sqlSession.close();
        System.out.println(order);
        
    }

}