JOpenID is an OpenID 2.0 Java 5 implementation for OpenID sign on.JOpenID is a very lightweight implementation for OpenID 2.0, about 50KB including source & binary.JOpenID only needs JDK 1.5 (...
JOID lets you create both OpenID 2.0 relying parties and identity providers.See the JavaOne 2007 presentation on OpenID and JOID.The Introduction page shows you how to use it.