Symfony2不会在会话中保存SecurityContext :: LAST_USERNAME

Question

我想获取会话中保存的last_username以在登录表单中使用它，但$ session-＆gt; get（SecurityContext :: LAST_USERNAME）始终为null

这是我的代码：

Config.yml

framework:
    #esi:             ~
    translator:      { fallback: %locale% }
    secret:          %secret%
    router:
        resource: "%kernel.root_dir%/config/routing.yml"
        strict_requirements: ~
    form:            ~
    csrf_protection: ~
    validation:      { enable_annotations: true }
    templating:
        engines: ['twig']
        #assets_version: SomeVersionScheme
    default_locale:  %locale%
    trusted_proxies: ['127.0.0.1']
    session:
      cookie_lifetime: 31536000
    fragments:       ~

登录操作：

  public function loginAction(Request $request)
    {
        $session = $request->getSession();
        ld( $session->get(SecurityContext::LAST_USERNAME));

        if ($request->attributes->has(SecurityContext::AUTHENTICATION_ERROR)) {
            $error = $request->attributes->get(
                SecurityContext::AUTHENTICATION_ERROR
            );
        } else {
            $error = $session->get(SecurityContext::AUTHENTICATION_ERROR);
            $session->remove(SecurityContext::AUTHENTICATION_ERROR);
        }

        return array(
            'last_username' => $session->get(SecurityContext::LAST_USERNAME),
            'error' => $error
        );
    }

错误是什么时候？

由于

此致