Hey guys, I’m currently developing a MMoRPG engine in Java, and I recently read about a thing called java webstart. I was going to make the client a download, but now I’m thinking I should do this instead (or make both…) Applets are too limiting, so that out of the picture. If I made a webstart, would I have to edit all the source code to work with it?
Thanks,
Willie 
No. Webstart is very easy to integrate with a Java desktop application. I would definitely recommend using it, but you can wait if you want without having to worry about it.
Okay, sweet. Right now I just have .bat files that execute commands to run the program.
While it can be easy to integrate with a Java app it can be a lot trickier to integrate with your build system or whatever release management process you may have in play.
I would highly recommend spending the time to learn it well and integrate it properly (instead of a hack-job) the very first time you need it (even for something as trivial as a demo to the java-gaming.org crowd). It’ll save you a ton of time in the long run.
I agree with loom_weaver, you can even use a build tool (ANT, Maven, etc…) to generate your JNLP file(s).
If you read files from disk you will have to use getResourceAsStream instead of File and similar classes. That took me some work to change.