04_解决字段名与实体类属性名不相同的冲突

1 准备表和数据

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);

2 定义实体类：表的字段和实体的属性不一致

public class Order {
	private int id;
	private String orderNo;
	private float price;
}

3 解决方法

3.1 通过查询的别名

<!-- 通过查询字段的别名来对应 -->
<select id="getOrder" parameterType="int" resultType="Order">
   SELECT order_id id, order_no orderNo, order_price price FROM orders WHERE order_id=#{id}
</select>

测试

@Test
	public void test1(){
		SqlSessionFactory factory = MybatisUtils.getFactory();
		SqlSession session = factory.openSession();
		
		String statement = "cn.imentors.mybatis.test4.orderMapper.getOrder";
		Order order = session.selectOne(statement , 2);
		System.out.println(order);
	}

3.2 通过resultMap

<resultMap type="Order" id="getOrder2Map">
	<id property="id" column="order_id"/>
	<result property="orderNo" column="order_no"/>
	<result property="price" column="order_price"/>
</resultMap>
<select id="getOrder2" parameterType="int" resultMap="getOrder2Map">
	SELECT * FROM orders WHERE order_id=#{id}
</select>

• resultMap : 封装一些映射关系
  
•  id : 专门针对主键
  
• result : 针对一般字段
  

测试

@Test
	public void test2(){
		SqlSessionFactory factory = MybatisUtils.getFactory();
		SqlSession session = factory.openSession();
		
		String statement =  "cn.imentors.mybatis.test4.orderMapper.getOrder2";
		Order order = session.selectOne(statement , 2);
		System.out.println(order);
	}

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