I had a look at the Facebook integration in Tonr 2. While this is a nice example of how to request resources from a provider once you're authenticated against the consumer I think the second use case is just as likely: use an OAuth provider to log into consumer.
Example: http://stackoverflow.com/users/login -> using Facebook
So, the question is how I could make use of
configured in applicationContext.xml for login?
<!--apply the oauth client context-->
<oauth:url pattern="/facebook/**" resources="facebook"/>
<!--define an oauth 2 resource for sparklr-->
<oauth:resource id="sparklr" type="authorization_code" clientId="tonr"..