Eror downloading a XLS file on the portal hosted struts/j2EE application

Question

guys,
1st of all please bare with for writing such a huge mail but to explain the scenario i had to do this.
i am trying to download a XLS file from the web application (struts/J2EE) hosted on the portlet.
on my portlet i have few text boxes and a button.
onlcik of the buton there are few validation javascripts and if the valdatin is thrugh then the form is submitted.
there are 2 ways i can submit the form to the struts action class.
both approaches have some problem or the other.
Apporach 1
var postUrl = document.getElementById('getReportURL_$$PORTLET_ID$$').innerHTML;
var post = new PTHTTPPOSTRequest(postUrl, form, handleInlinePostResponse_$$PORTLET_ID$$);
post.invoke();
this is like a AJAX request post where the response comes back in the function handleInlinePostResponse_$$PORTLET_ID$$ which can be then handled.
Problems
1. as from action class i am trying to send a XLS file, i am writing the byte stream of the XLS file on the output stream of the response. when the response reaches the function handleInlinePostResponse_$$PORTLET_ID$$ on portlet jsp it gives me an javascript exception 'End of file reached in invalid state for current encoding' but while sending the response i am encoding the byte stream.
the code snippet from the action class is as below
response.reset();
response.resetBuffer();     
response.setHeader("Content-disposition", "attachment; filename=" + reportData.getFilename());
response.setCharacterEncoding("UTF-8");
response.setContentType("application/vnd.ms-excel");
response.getOutputStream().write(reportData.getContent()); //byte[] form of the XLS file
return null; //as we write on the response out stream the response is already commited hence the return null has no significance.
2. in case of the any exception on server side this approach is helpful as the error content jsp is rendered in to the portlet from where the action was fired.
Approach 2
form.action = "<pt:url xmlns:pt='http://www.plumtree.com/xmlschemas/ptui/' pt:href='downloadCommercialXLSReport.do'/>" ;
form.submit();
This approach is normal for submitting any struts from bean to the struts action class (i know this is not a aprropriate way to submit d form through portlet as it submits whole page inclusding all the portlet data)
Problems
1. here in case of the sucess the XLS file is returned to the browser which openes a browser specific dialogue box having 'Save' 'Open' and 'Cancel' buttons to save/open the XLS file. (please note no javascript exception occurs here as approach one as the byte streeam content is returned to the browser directly and not to any post response handler function as handleInlinePostResponse_$$PORTLET_ID$$)
2. But here the problem is in case of any sever side exception the error jsp is rendered on whole browser page and not in portlet which is kinda goofy.
so now i am in a catch 22 scenario each approach has 1 problem either in success or in failure flow.
can sombody suggest me a way out from this as i desperately need to download a XLS file.
lemme kno if anybody has done a similar download stuf through portal server.
regards,
Sush

Answer 1

i have done this before although it was in .net. try the first approach but first pop to a new window....the xls response has to be the only response to the browser or else the browser will take the other bytes returned as garbage and call the stream corrupt. let me know how this goes for you.
if you still have problems i can post the code that worked for me. it is in c# but looks very similar.