I had a similar problem a while back and got a handle on the UploadedFile Object by doing this:

 

public void uploadFile(String serverid) {
        try {          
                String clientid = (String)FacesContext.getCurrentInstance().getApplication().getVariableResolver().resolveVariable(FacesContext.getCurrentInstance(), "#{id:"+serverid+"}");
                HttpServletRequest hsr = (HttpServletRequest)FacesContext.getCurrentInstance().getExternalContext().getRequest();
                Map map = hsr.getParameterMap();
                UploadedFile uf = ((UploadedFile)map.get(clientid));
                File fi = uf.getServerFile();
                // Do whatever you want with the file

            }
               catch (Exception e) {
                   System.out.println(e);
               }
        }