*Mapper.xml文件头

<?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">

<mapper namespace="dao">
    <select id="方法" resultType="pojo">
        select * from user ;
    </select>
</mapper>