Java Web Start - update SOME users?

Updates via JWS are too much pain and work for help desk, because on every release a few per cent users "get stuck" in the middle and are unable to launch the application without reinstall. We're looking for a way to update only some u开发者_如何转开发sers and then incrementally push the new version to more of them.

I don't see a way to do this directly with JNLP. Ideas we have so far include:

• Place new jar(s) in the web directory. Update JNLP launch file to these new jars. After an hour, revert JNLP. Question: Does JNLP specify what will happen to users who have already updated and now hit the "downgraded" launch file? (Hard data please)
• Have 5 JNLP launch files and have help desk reinstall the application everywhere. Then update one file at a time (i.e. 20% users at a time).
• Implement a server-side solution, such as a CGI script on top of Apache, that will serve different revisions of the JNLP launch file to different users based on their IP.

What downsides do you see in these options? What else can we consider?

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I don't understand why some users get stuck. What do you mean by re-install? I just have users launch from the web site. Nothing gets installed. They can place the JNLP file on the desktop if they like, but the software is still not "installed" in the traditional sense.

For my application, I have it check for updates in the background:

This means that every time the program is launched, the client computer checks the locally stored version against the jar on my server. Downloading the latest version happens behind the scenes and the next time the program is launched, the new version is used. No one gets stuck.