How can I pass Java Web Start configuration properties via command line or Runtime.getRuntime().exec()?

Question

I have an application that launches javaws using

Runtime.getRuntime().exec(new String[] {[javawsPath], [jnlpPath]}, null);

That works fine. However, I now need to also give it the proxy settings (host and port), which I will prompt the user for before launching javaws.

How can I do this? I tried adding

"deployment.proxy.http.host=[url]", "deployment.proxy.http.port=[port]"

to the String[] in exec(), but that gives me an invalid argument exception.

Any ideas?

Thanks!