可以'；t使用UsernamePasswordToken在Symfony2中启动会话

Symfony2.4使用UsernamePasswordToken登录时出现错误，我快要疯了。。。

我在我的网站上用他们的URL和他们用户的哈希自动登录用户。行动非常简单，我唯一想做的（经过一些检查）是：

$token = new UsernamePasswordToken($user, $user->getPassword(), 'secured_area', $user->getRoles());
$this->get('security.context')->setToken($token);

有了这个，在某些情况下它是有效的（当我尝试时，它总是有效的…），但在一些情况下不起作用。。。这种情况下的日志显示：

[2014-10-30 15:47:25] request.INFO: Matched route "_my_route" (parameters: "_controller": "MyController", "url": "my-url", "hash": "2f5fccc7b5fc2d41bbc3e1e469655f24f540e383", "_route": "_my_route") [] []
[2014-10-30 15:47:25] security.INFO: Populated SecurityContext with an anonymous Token [] []
[2014-10-30 15:47:25] security.DEBUG: Write SecurityContext in the session [] []
[2014-10-30 15:47:25] request.CRITICAL: Uncaught PHP Exception RuntimeException: "Failed to start the session because headers have already been sent by "/route/app/bootstrap.php.cache" at line 1365." at /route/app/cache/prod/classes.php line 119 {"exception":"[object] (RuntimeException: Failed to start the session because headers have already been sent by '"/route/app/bootstrap.php.cache'" at line 1365. at /route/app/cache/prod/classes.php:119)"} []
[2014-10-30 15:47:25] security.DEBUG: Write SecurityContext in the session [] []

为什么标头已经发送？为什么只有在某些情况下？有人知道什么时候经常发生这种情况？

我尝试了很多事情：检查在此之前是否没有打印任何字符，更改安全性中的防火墙。yml，将会话放在磁盘文件中。。。

我认为一切都好。

我的用户实体：

class MyUser implements UserInterface, 'Serializable
{
...
/**
 * Serializes the user.
 *
 * The serialized data have to contain the fields used byt the equals method.
 *
 * @return string
 */
public function serialize()
{
    return serialize(array(
        $this->id,
        $this->password,
        $this->email
    ));
}
/**
 * Unserializes the user.
 *
 * @param string $serialized The serialized string
 *
 * @return void
 */
public function unserialize($serialized)
{
    list(
        $this->id,
        $this->password,
        $this->email
    ) = unserialize($serialized);
}
...

Security.yml

security:
encoders:
    Symfony'Component'Security'Core'User'User: plaintext
    MyProject'PublicBundle'Entity'MyUser:
        algorithm:   sha1
        iterations: 1
        encode_as_base64: false
role_hierarchy:
    ROLE_USER:        ROLE_PENDING
    ROLE_ADMIN:       ROLE_USER
    ROLE_SUPER_ADMIN: [ROLE_USER, ROLE_ADMIN, ROLE_ALLOWED_TO_SWITCH]
providers:
    main:
        entity: { class: MyProject'PublicBundle'Entity'MyUser, property: email }
firewalls:
    dev:
        pattern:  ^/(_(profiler|wdt)|css|images|js)/
        security: false
    secured_area:
        pattern:    ^/
        anonymous: ~
        form_login:
            login_path: /login
            check_path: /login_check
            failure_path: /login
            username_parameter: email
            password_parameter: password
            default_target_path: /login-redirect
        logout:
            path:   /logout
            target: /
        remember_me:
            key:      "aSecretKey"
            lifetime: 321408000
            path:     /
            domain:   %domain%

config.yml（会话部分是在第一次错误后添加的）

framework:
secret:          "%secret%"
router:
    resource: "%kernel.root_dir%/config/routing.yml"
    strict_requirements: ~
form:            ~
csrf_protection: ~
validation:      { enable_annotations: true }
templating:
    engines: ['twig']
default_locale:  "%locale%"
trusted_hosts:   ~
trusted_proxies: ~
session:
    handler_id: session.handler.native_file
    save_path: "%kernel.root_dir%/sessions"
fragments:       ~
http_method_override: true