The Java Deployment team needs support for per connection proxy in URLs for the following reason:

"When auto proxy script is specified, plugin needs to use no proxy to
download it, and in turns to use the script to evaluate proxy for future
connection. This works in the initialization phase even if no additional
API support. However, at any given time when the app is running, users
may detect to ask plugin/webstart to refresh the proxy. We will then
need to download the auto proxy script again with the ProxySelector
already installed. This is why I want per connection proxy. Also, applet
developers in the enterprise may want to make connection with a specify
proxy, so they don't have to worry about if the proxy in the client
machine is completely setup. " -- Stanley