Write the
servlet so that when you POST all the information, it fetches the Excel document from the database and stores it in a temporary directory in web space under a name which is an MD5 checksum or some other long
string of nonsense characters. Then set a HttpSessionBindingListener to delete the file when the session expires. Make sure that temporary directory doesn't allow indexing. Finally, return the URL as the servlet's response.
Now the
applet POSTs to the servlet and gets that URL, then uses showDocument() to open the spreadsheet in the browser.
Still waiting for that pig pen to get shoveled out.