1、编写mapper接口
public interface EmployeeMapper {
public Employee getEmpById(Integer id);
}
2、编写sql映射文件,配置了每一个sql以及sql的封装规则
<?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">
<!--namespace:名称空间,对应mapper接口的全类名-->
<mapper namespace="com.sangyu.mapper.EmployeeMapper">
<!--
id:唯一标识
resultType:返回值类型,对应的Bean类型
{#id}:从传递过来的参数中取出id值
select 中增加别名,防止因为mysql中的字段与bean中的不对应,导致该字段查询出来的结果为空
-->
<select id="getEmpId" resultType="com.sangyu.bean.Employee">
select id,last_name lastName,email,gender from tbl_employee where id = #{id}
</select>
</mapper>
3、查询过程:
public class MyBatisTest {
@Test
public void Test() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); // 根据xml创建sqlSessionFactory
SqlSession session = sqlSessionFactory.openSession(); // 2. 从 SqlSessionFactory 中获取 SqlSession 的实例,SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句
try {
// 3. 获取接口的实现类对象
EmployeeMapper mapper = session.getMapper(EmployeeMapper.class);
Employee employee = mapper.getEmpById(1);
System.out.println(employee);
}finally {
session.close();
}
}
}