exam-api/target/classes/mapper/sys/system/SysDictMapper.xml

<?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="com.ydl.exam.modules.sys.system.mapper.SysDictMapper">

    <select id="findDict" resultType="String">
        SELECT ${text} FROM ${table} WHERE ${key}=${value} LIMIT 1
    </select>

</mapper>