The goal with this exercise is to have a running example of an OpenID login on a simple Spring application, using Google as the OpenID Provider. Note that the application will be running on Google App Engine and that Spring Roo is only used for simplicity of creating the project files. Any Spring-based application could use the same implementation. First of all, create a simple project using Spring Roo (or any equivalent framework), including the default security setup: project --topLevelPackage com.technowobble persistence setup --provider DATANUCLEUS --database GOOGLE_APP_ENGINE entity --class ~.domain.MyEntity field string --fieldName name controller all --package com.technowobble.controller security setup This setup only provides us with a form-login, which is not what we wanted. So what about OpenID? Well, if it wasn't for Google App Engine, I would happily have added an <openid-login>-tag to applicationContext-security.xml, but things are never that easy, are the...