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