<select id="paixuList" parameterType="string" resultMap="MessageResult">

      select ID,COMMAND,DESCRIPTION,CONTENT from message 

      order by ${_paremeter} desc;

  </select>

运行，显示错误“There is no getter for property named '_paremeter' in 'class java.lang.String'”，好奇怪阿 ，不是基本类型，就用 '_paremeter'吗，怎么会找不到呢