How to set and get Session in Symfony2?

SessionInterface object set and get method is used to set and get sessions in Symfony2.Below look below example:

public function sessionAction(SessionInterface $session)

{

    // store an attribute for reuse during a later user request

    $session->set('user_id', 5);

    // get the attribute set by another controller in another request

    $user_id = $session->get('user_id');  

}