jucai/app/Admin/Controllers/Admin/AuthController.php

<?php
namespace App\Admin\Controllers\Admin;

use Illuminate\Routing\Controller;
use Illuminate\Support\Facades\Auth;

class AuthController extends Controller
{
    /**
     * Show the login page.
     *
     * @return \Illuminate\Contracts\View\Factory|Redirect|\Illuminate\View\View
     */
    public function getLogin()
    {
        if ($this->guard()->check()) {
            return redirect($this->redirectPath());
        }

        return view('admin.login');
    }

    /**
     * Get the post login redirect path.
     *
     * @return string
     */
    protected function redirectPath()
    {
        if (method_exists($this, 'redirectTo')) {
            return $this->redirectTo();
        }

        return property_exists($this, 'redirectTo') ? $this->redirectTo : config('admin.route.prefix');
    }


    /**
     * Get the guard to be used during authentication.
     *
     * @return \Illuminate\Contracts\Auth\StatefulGuard
     */
    protected function guard()
    {
        return Auth::guard('admin');
    }
}