Laravel 5 input::get error

为什么会出现此错误？我试图添加使用Illuminate'Http'Request;但是同样的错误？$username = $request->input('username');也和$username = Input::get('username');一样吗？

我得到的错误是：

FatalErrorException in LoginController.php line 22: Class 'App'Http'Controllers'Input' not found

class LoginController extends Controller {
  // Display the login form
  public function showLogin()
  {
    return View::make('login');
  }
  // Process submission of the login form by verifying user’s credentials
  public function processLogin()
  {
    $username = Input::get('username');
    $password = Input::get('password');
    if ($username === 'prince' && $password === 'c@spiAN') {
      return 'Access granted!';
    } else {
      return 'Access denied! Wrong username or password.';
    }
  }
}