如何在symfony2中的语言var中存储会话

How to store session in language var ?
My parameters.ini sets default local

locale = en

My config.yml sets default locale

translator:      { fallback: %locale% }
default_locale:  "%locale%"

And I have changed language in language controller

public function languageAction(Request $request)
{

        $request = $this->getRequest();
        $request->setLocale('fr_FR');


        // BOTH CODE TRY IT ABOVE AND BELLOW BUT NOT RUN ANY ONE


        $session = $this->get('session');
        $session->set('locale', 'fr_FR');


}

I have set fr_FR language in session "locale", and I have echo "Locale" other Controller so get value "en" inserted of "fr_FR"

Following way I have echo locale value

class galleryController extends Dashboard
{
    public function indexAction(Request $request)
    {

        $request = $this->getRequest();
    echo $request->getLocale(); 

    **or**

    $session = $this->get('session');
        echo $session->get('locale');

    }
}

How to set session in setLocale and getLocale in "'fr_FR' lang