Php Laravel show类签名不存在

嗨，我的Laravel Rest API应用程序有问题，每当我在我的邮递员中访问localhost:8000/API/login时，我都会这么说

（1/1）ReflectionException类签名不存在

这是我的artisan路线：api/登录列表

POST | api/登录| | App\Http\Controllers\api\UserController@login| api

这是我的api路线

<?php

use Illuminate\Http\Request;

Route::middleware('auth:api')->get('/user', function (Request $request) {
    return $request->user();
});

Route::post('oauth/token', '\Laravel\Passport\Http\Controllers\AccessTokenController@issueToken');


Route::group(['namespace' => 'Api'], function () {
    Route::post('/login', 'UserController@login');
});

---

我认为您可以在laravel中使用示例进行自定义身份验证：
我需要解决为什么laravel会抛出该错误以及我应该怎么做。链接到某个教程并不是一个答案。链接可能会断开。
<?php

namespace App\Http\Controllers\Api;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;
use Illuminate\Support\Facades\Auth;
use App\User;
use Response;

class UserController extends Controller
{
    public function __construct()
    {
        $this->content = array();
    }

    public function login()
    {
        if (Auth::attempt(['email' => request('email'), 'password' => request('password')])) {
            $user = Auth::user();
            $this->content['token'] =  $user->createToken('Pizza App')->accessToken;
            $status = 200;
        } else {
            $this->content['error'] = "Unauthorised";
             $status = 401;
        }

        return response()->json($this->content, $status);    
    }
}