I've be looking for a while now but only found old or incomplete projects related to this purpose.
Velruse is Python library for identification thanks to OpenId, Google account, Facebook connect, etc .. and I didn't find the equivalent for Java but I guess it may exist I'm just not looking in the good direction!
If anyone has experienced this before could he share his knowledge on this.
What I've found:
OpenID4Java : Seems to be only for openID
JOpenID : Seems to be only for openId
OpenId Selector : Javascript client side implementation providing openID, could be coupled with one of the previous java library on the server side.
You can use Velruse as a service, you don't need to know python. You only need to connect and velruse does the magic for you :)