Mapper.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE mapper

  PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

  "https://mybatis.org/dtd/mybatis-3-mapper.dtd">

<!--namespace 绑定一个对应的 Dao (Mapper) 接口 -->

<mapper namespace="org.mybatis.example.BlogMapper">

<!--SQL 语句头标签 -->

<!--select: 查询语句，id: 对应接口的方法名，parameterType: 参数类型，resultType: 返回值类型 -->

  <select id="selectBlog" parameterType="map" resultType="Blog">

    select * from Blog where id = #{id}

  </select>

</mapper>