使用Symfony Security的简单登录表单

我尝试使用本教程进行登录表单：http://symfony.com/doc/current/cookbook/security/form_login_setup.html

所以，现在我的 security.yml 文件看起来像：

security:
    providers:
        in_memory:
            memory:
                users:
                    ryan:
                        password: ryanpass
                        roles: 'ROLE_USER'
                    admin:
                        password: kitten
                        roles: 'ROLE_ADMIN'
    encoders:
      Symfony'Component'Security'Core'User'User: plaintext
    firewalls:
        login_firewall:
            pattern:   ^/login$
            anonymous: ~
        secured_area:
            pattern:    ^/
            anonymous: ~
            form_login:
              login_path: login
              check_path: login
        dev:
            pattern: ^/(_(profiler|wdt)|css|images|js)/
            security: false
    access_control:
        - { path: ^/login, roles: IS_AUTHENTICATED_ANONYMOUSLY }
        - { path: ^/, roles: ROLE_USER }

安全控制器：

class SecurityController extends Controller
{
    /**
     * @Route("/login", name="login")
     */
    public function loginAction(Request $request)
    {
        $authenticationUtils = $this->get('security.authentication_utils');
        // get the login error if there is one
        $error = $authenticationUtils->getLastAuthenticationError();
        // last username entered by the user
        $lastUsername = $authenticationUtils->getLastUsername();
        return $this->render(
            'AppBundle:Security:login.html.twig',
            array(
                // last username entered by the user
                'last_username' => $lastUsername,
                'error'         => $error,
            )
        );
    }
}

所以基本上，它不能正常工作。发送登录表单后没有任何反应，我不知道为什么。我认为安全性的配置是错误的。有人可以帮助我吗？我不知道出了什么问题。