How to handle long running web service operations?

Question

I have to create a Java EE application which converts large documents into different formats. Each conversion takes between 10 seconds and 2 minutes. The SOAP requests will

Answer 1

Since this almost all done server-side, there isn't much a client can do besides poll the server somehow for updates on the status.

#1 is OK, but users get impatient really fast. "A few minutes" is a bit too long for most people. You'd need HTTP Streaming to implement #3, but I think that's overkill.

I would just go with #2.