Mybatis java.lang.UnsupportedOperationException 错误

mapper 语句如下

<select id="getDeptIds"
            resultType="java.util.List"
            parameterType="java.lang.Long">
        SELECT
          dept_id AS deptId
        FROM
          sys_user_dept
        WHERE user_id = #{userId}
</select>

Dao 对应接口

 List<Long> getDeptIds(Long userId);

应将 mapper 中select 的属性resultType改成 java.lang.Long