Filter for triggering 'download' dialog..

Hello,

I'm working on a project where we send XML data to servlets.  The data can
be sent by a process that either opens a connection to the servlet and sends
it directly (via an HTTP POST method), or as an uploaded file via a form on
a web
page.  Now, what we need to do is if the XML data is sent via direct
connection and POST we send the data back as a "text/xml" content type.  If
the data is 'uploaded' via a form we send the response back as a file and
set the content-disposition like this:

reply.getMimeHeaders().setHeader("content-disposition", "attachment;
filename=download.xml");

The problem is that we want to move this functionality into a filter.  That
way we can have various servlets that can support the same capability
without copying code.  The *problem* is that if the response data is over a
certain size the content-dispostion is being ignored....  I inherited the
filter code from another programmer, and what seems to be happening is that
before we can change the content-disposition in the filter part of the data
has already been flushed out.  My question is, how do I buffer or "hold
back" the output stream that's now hitting the filter code on the way back
to the client and modify the content-disposition accordingly.

I've included code snippets of our approach so you can see what we're
doing...  Any suggestions would be much appreciated.  I've thought about
perhaps making a custom HttpServletResponseWrapper and possibly buffering
the output there until the filter is ready to work with it

    private String MULTIPART_CONTENT_TYPE = "multipart/form-data";
    private String XML_CONTENT_TYPE = "text/xml";

(in doFilter)

    HttpServletRequest httpServletRequest = (HttpServletRequest) request;
    String contentType = httpServletRequest.getContentType();
    if (contentType == null) return;
    boolean fileUploadDownload = contentType.indexOf(MULTIPART_CONTENT_TYPE)
!= -1;
    //wrapperX extends HttpServletRequestWrapper and includes a few
overridden bethods to
    //support our efforts - among them are setContentType and setInputStream
    WrapperX wrapperX = new WrapperX((HttpServletRequest)request);
    if (fileUploadDownload) {
        wrapperX.setContentType(XML_CONTENT_TYPE);
        wrapperX.setInputStream(new
WrapperS(getInputStream(httpServletRequest)));
    }

    filterChain.doFilter(wrapperX, response);

    if (fileUploadDownload) {
        HttpServletResponse httpServletResponse =
(HttpServletResponse)response;
        counter++;
        httpServletResponse.setHeader("Content-Disposition:","attachment;
filename=SubmitResponse_" + counter + ".xml" );

System.out.println("getBufferSize()"+httpServletResponse.getBufferSize());
    }


--
David Orriss Jr.

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