I'm the main developer of Tudu Lists, which is the demo application for the Spring book I wrote.
It's a demo application, featuring JPA + Spring + several front ends (Struts + DWR being the main one).
Lots of people are using it to build Spring-based applications (just have a look at the Sourceforge statistics, and we have more than 12,000 users registered on the demo server at http://tudu.ess.ch ), but I've had only very little feedback on the project architecture.
More specifically, I would be interested in people reviewing the "tudu-core" sub-project, which is the domain+service layer of the application.
Thank you for your help!