I want to implement user account system for my site just like this, http://getsatisfaction.com/login allowing the user to login using Facebook, Twitter, Google, Yahoo and the like. The site is built using Struts 2 + Spring + Hibernate.
Any Java libraries that would help me in building this kind of user account system?
You might want to look to JOpenID, it is an OpenID 2.0 Java 5 implementation for Google Federated Login. Also SocialAuth for google, yahoo, windows live, twitter and fb. Or maybe a look to JanRain Engage it is free up to 2,500 users.