解决字段名与实体类属性名不相同的冲突

因为java工程师定义实体类属性名的和数据库工程师所定义的字段名不一致，所以要解决不一致的冲突

1、目录结构

2、在数据库中建立相应的表并填入数据

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('aaaa', 23);
INSERT INTO orders(order_no, order_price) VALUES('bbbb', 33);
INSERT INTO orders(order_no, order_price) VALUES('cccc', 22);

3、定义实体类

package com.sxau.rjxy.MyBatis_test4;

public class Order {
	private int id;
	private String orderno;
	private float price;
	public Order(int id,String orderno,float price){
		this.id = id;
		this.orderno = orderno;
		this.price = price;
	}
	public Order(){}
	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;
	}
	@Override
	public String toString() {
		return "Order [id=" + id + ", orderno=" + orderno + ", price=" + price + "]";
	}
	public void setPrice(float price) {
		this.price = price;
	}
	
}

OrderMapper.xml配置文件

select中的resultMap名应该与下面的resultMap中的id名对应

<?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.sxau.rjxy.MyBatis_test4.orderMapper">
	<select id="getOrder" parameterType ="int" 
	resultType="Order" resultMap="orderResultMap">
		select * from orders where order_id =#{id}
		 <!--select order_id id,order_no orderno,order_price price from orders where order_id =#{id}
		 -->
	</select>
	
	 <resultMap type = "com.sxau.rjxy.MyBatis_test4.Order" id="orderResultMap">
		<id property="id" column="order_id" />
		<id property="orderno" column="order_no" />
		<id property="price" column="order_price" />
	</resultMap>
</mapper>

方法二

将select * from orders where order_id =#{id}注解。将下面的那句select解除注解并删除resultMap也可以实现。

4、conf.xml配置文件

<?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>
	<properties resource="db.properties" >
	</properties>
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="${driver}" />
				<property name="url" value="${url}" /><!-- 数据库名可更改 -->
				<property name="username" value="${username}" />
				<property name="password" value="${password}" /><!-- 密码可更改 -->
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="com/sxau/rjxy/MyBatis_test/userMapper.xml" />
		<mapper resource="com/sxau/rjxy/MyBatis_test2/userMapper1.xml"  /><!-- 这个是右键userMapper.xml选择 copy qualified Name复制，并删除com之前的东西-->
		<mapper resource="com/sxau/rjxy/MyBatis_test3/userMapper.xml"  />
		<mapper resource="com/sxau/rjxy/MyBatis_test4/orderMapper.xml" />
	</mappers>
</configuration>

5、测试类

package com.sxau.rjxy.MyBatis_test4;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import com.sxau.rjxy.MyBatis_test2.MyBatisUtils;

public class Test4 {
	public static void main(String[] args) {
		
		//构建sqlSession的工厂
		SqlSessionFactory factory = MyBatisUtils.getFactory();
		//创建能执行映射文件中sql的sqlSession
		SqlSession session = factory.openSession();
		//映射sql的标识字符串
		String statement = "com.sxau.rjxy.MyBatis_test4.orderMapper.getOrder";
		//执行查询返回一个唯一user对象的sql
		Order order = session.selectOne(statement, 1);
		System.out.println(order);
	}
}