I have a very general question regarding java desktop-gui-applications.
My Experience: In the last years i have developed a number of desktop-applicati
May I suggest to have a look at Eclipse Scout? It is Java/Eclipse based and available under the EPL.
Scout primarily addresses building business applications. With its clean separation of the client ui model from the actual ui rendering you have the options to run your app with Eclipse SWT, Swing, or web application (based on Eclipse RAP, this will come with the Juno release).
Regarding your question to field validation i am confident that you will find the provided mechanism (overwrite method execValidate() of the desired fields) comfortable to use.
Please have a look at the available tutorials on our wiki page. In case you need a client only solution (no backed server) also consider this howto.
For questions related to Eclipse Scout please use the project forum.
Hope this helps.