In Symfony2 you can work with multiple entity managers and use something like the code below:
$em = $this->get('doctrine')->getManager();
$em = $this->get('doctrine')->getManager('default');
$customerEm = $this->get('doctrine')->getManager('customer');
We can inject the default manager to any service by using:
"@doctrine.orm.entity_manager"
How can you inject non-default entity managers into services?
If your entity managers config name is non_default
then you can reference it as @doctrine.orm.non_default_entity_manager