Mybatis中parameterType为string和对象的区别

 <select id="selectedUser" resultType="com.xxx.User" parameterType="String">
        SELECT user_Id AS userId, user_Name AS userName FROM users WHERE user_id = #{userId} AND user_name = #{userName}
</select>

List<User> selectedUser(@Param("userId") String userId,@Param("userName") String userName);

<update id="updateUser" parameterType="com.xxx.user">
        UPDATE tb_user SET user_name=#{userName},user_sex=#{userSex}
        WHERE user_id=#{userId}
</update>

int updateUser(User user);