Okay. Then you're just running it in the normal way. (Your reference to "running in the browser" confused me.) Anyway it's just an ordinary
Java application, so you connect to the database in the normal way. If your code fails to connect to the database, do you have any way of finding out (a) that it failed to connect, and (b) the errors which caused it to fail? If you don't, then your first step should be to fix that problem.
I'm guessing that probably you just need to sign the application, but it's certainly possible that (for example) you hard-coded "localhost" as the location of the database server, and that worked OK in your
testing because your test machine was the database server but now it doesn't work in the wild. Or there could be any number of other problems.