Add support for OpenID authentication
It is necessary to remember authentication tokens if SSO systems like OpenID should work.
Such a token storage system can then be also used with OAuth.
Authenticate using OpenID, but store authentication token using the normal cookie auth mechanism. Every subsequent request to OpenID resource triggers an OpenID login from scratch, no OpenID-related cookies are stored to support this.
Enable your Java Web applications to use OpenID authentication
Write an OpenID Provider for single sign-on authentication