In this post I'll combine the GWT and Spring Security integration from http://technowobble.blogspot.com/2010/05/gwt-and-spring-security.html and the Open-ID using Spring Security from http://technowobble.blogspot.com/2010/06/using-spring-securitys-openid.html . I'm assuming you've read them before reading further... :) I was also inspired by http://www.sociallipstick.com/?p=86 and http://code.google.com/p/dyuproject/wiki/OpenidLoginWithoutLeavingPage to get this working with a pop-up as my sample application is based on GWT - hence, I don't want to direct the user to another page and loose the application state etc. I'm also showing how to exchange Open-ID attributes with e.g. Google. As with the previous blogposts, the sample application is runnable on Google App Engine. With no further ado, this is basically what is needed to add Open-ID support to my previous sample application: From my second post, add Openid4javaFetcher, MyHttpCacheProvider and OpenI...