The OAuth2 Framework allows you to protect your web resources using the next generation OAuth, (http://oauth.net/2/) as well as accessing OAuth2 protected resources, most notably the Facebook Graph API. The API consists of libraries for building your own OAuth2 server as well as client side access. The standard is still in draft mode so expect some level of changes. Currently version 10 of the OAuth 2 specification is the one being supported.
The framework is implemented in Java on top of Restlet.org HTTP framework.
It can execute on all platforms that Restlet is available on and it is validated using Java SE, EE and Android.
Donated to Restlet.org as an open source project with very generous open source license for reuse.