Symfony 2 : multiple and dynamic database connection

I am quite new to SF2 and I was wondering how I could manage connections to severals databases into ONE bundle. For the moment I have this solution - which works fine - but I don't know if it is the right way to do it....

in myBundle\Ressource\config\config.yml :

doctrine:
dbal:
    default_connection:       default
    connections:
        default:
            dbname:           SERVER
            user:             root
            password:         null
            host:             localhost
        client:
            dbname:           CLIENT_134
            user:             root
            password:         null
            host:             localhost
orm:
    default_entity_manager:   default
    entity_managers:
        default:
            connection:       default
            mappings:
                MyBundle: ~
        client:
            connection:       client
            mappings:
                MyBundle: ~

And then, in order to switch to one of the BD or the other, I do :

$O_ressource=  $this->get('doctrine')->getEntityManager('client');
$O_ressource=  $this->get('doctrine')->getEntityManager('default');

So guys, do you think it is a good way to manage this?

And my second question is :

how to set up dynamic database connection? I mean I have 100 databases in my system and I can't set all them in my config.yml file. So I would like to be able to change database on the fly.

Thanks for the help!