The only way you can get the IP of the user in a place where you can access the HttpRequest. Since Vaadin abstracts this away from you, you should hook into a class where you have access to this. You can override the org.activiti.explorer.ui.login.DefaultLoginHandler (wired in in activiti-standalone-context.xml) and override the method: public void onRequestStart(HttpServletRequest request, HttpServletResponse response) or even better, the Authenticate(HttpReq…) method.
In this method, you can (for example) return a subclass of the LoggedInUserImpl that has a getter/setter of the IP, which is extracted and set from the HTTPRequest. Another way to store the IP is to use a thread-local which can be statically accessed from the code you have running in the explorer…