php – 关于如何构建传统登录表单的Symfony 3错误

问题是我总是回到登录表单,并且无法找到我所缺少的内容.
我正在使用Synfony 3版本.
谢谢你的帮助:)

security:
    encoders:
        SymfonyComponentSecurityCoreUserUser: plaintext
    providers:
        in_memory:
            memory: 
                users:
                    ryan:
                        password: ryanpass
                        roles: 'ROLE_USER'
                    admin:
                        password: admin
                        roles: 'ROLE_USER'
    firewalls:
        dev:
            pattern: ^/(_(profiler|wdt)|css|images|js)/
            security: false


        home:
            pattern: ^/home$
            form_login:
                login_path: login
                check_path: login
                always_use_default_target_path: true

        main:
            anonymous: ~


=========== routing
login:
    path:   /login
    defaults:  { _controller: AppBundle:Security:login }

btw_user:
    resource: "@BTWUserBundle/Resources/config/routing.yml"
    prefix:   /

btw_menus:
    resource: "@BTWMenusBundle/Resources/config/routing.yml"
    prefix:   /

app:
    resource: "@AppBundle/Controller/"
    type:     annotation

btw_home:
    resource: "@BTWHomeBundle/Resources/config/routing.yml"
    prefix:   /


============ controller
namespace AppBundleController;

use SymfonyBundleFrameworkBundleControllerController;
use SymfonyComponentHttpFoundationRequest;
use SensioBundleFrameworkExtraBundleConfigurationRoute;


class SecurityController extends Controller {

    public function loginAction(Request $request) {
        //var_dump($request);

        $authenticationUtils = $this->get("security.authentication_utils");
        //var_dump($_POST);
        // get the login error if there is one
        $error = $authenticationUtils->getLastAuthenticationError ();
        var_dump($error);
        // last username entered by the user
        $lastUsername = $authenticationUtils->getLastUsername();
        var_dump($lastUsername);
        return $this->render ( 'security/login.html.twig',array(
            // last username entered by the user
            'last_username' => $lastUsername,'error'         => $error,));
    }
}