As you tell me now you have a JAvaapplication. Users download this to their machine, am i right?? They open the application on their machine and this application is going to contact the SQL server for it's data, hope i'm still right here.. :) This means all SQL data will be pushged over the line to your client.. The server will be receving data requests from all local machines.
If you rebuild the application to a web application, all users will ne accessing the web server (which is build for these kinds of things) and the webserver will be the only server reqeusting info from your SQL server.. Not only is it much more secure, it is also a lot less restraining to your network environment..
I am making some assumptions here so i just might be wrong..