04_ Resolving conflicts where field names differ from entity class property names

1 Preparing tables and data

  
 

   
  

  
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 Defining Entity classes: Table fields and entity properties are inconsistent

  
 

   
  

  
public class Order {
   
  

  
private int id;
   
  

  
private String orderNo;
   
  

  
private float price;
   
  

  
}
  
 

3 Workaround 3.1 Alias by query

  
 

   
  

  
<!-- 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>
  
 

Test

  
 

   
  

  
@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 by 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: Encapsulating Some mapping relationships
  
• ID: specifically for primary key
  
• Result: For general fields
  

Test

  
 

   
  

  
@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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04_ Resolving conflicts where field names differ from entity class property names