Mapper 作为 Java 方法和 SQL 语句之间的桥梁，来更好地去使用 SQL
准备数据源
创建
drop database if exists mybatis_demo;
create database mybatis_demo;
use mybatis_demo;
create table user (
id int auto_increment primary key,
username varchar(20),
age int,
score int
);
insert into user (id, username, age, score) values
(1,‘peter‘, 18, 100), (2,‘pedro‘, 24, 200),
(3,‘jerry‘, 28, 500), (4,‘mike‘, 12, 300),
(5,‘tom‘, 27, 1000);
在mybatis-config.xml配置文件中添加上对应的mapper配置
<!-- mapper配置 -->
<mappers>
<mapper class="mapper.UserMapper"/>
</mappers>
新建mapper包并新建UserMapper.java类
package mapper;
public interface UserMapper {
String selectUsernameById(Integer id);
}
添加SQL语句
@Select("SELECT username FROM user WHERE id = #{id}")
测试类usertest.java
@SuppressWarnings({"Duplicates"})
public class UserTest {
public static void main(String[] args) throws IOException, SQLException {
InputStream configuration = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(configuration);
SqlSession session = sqlSessionFactory.openSession();
UserMapper mapper = session.getMapper(UserMapper.class);
String username = mapper.selectUsernameById(1);
System.out.println("username: " + username);
session.close();
}
}