How to initiate file download

[tdsproule]

In my Seam 2.0.1 app I've created an in memory Excel file (as stream of bytes).  How do I go about initiating a file download via the browser from an action button so that browser does 'file download warning/where do you want to put it'? What sort of HTML/JSF do I serve up for this? 

I know this is probably easy but I can't find documentation that tells me how to do this.

Thanks
Todd

[svadu]

meta code:

/* your action */
public String download() {
          HttpServletResponse response = (HttpServletResponse)extCtx.getResponse();
          response.setContentType("application/octet-stream");
          response.addHeader("Content-Disposition","attachment;filename=" + FILE_NAME);

          PrintWriter writer = response.getWriter();

           /* DO YOUR THING (like writer.write) */

          // finish
          writer.flush();
          facesContext.responseComplete();
          writer.close();

          return "result;

}

[bidance]

i have mainly the same problem i m also using a seam action but i want to open the in memory file (stream of bytes) in the browser  i m actually  getting this exception
java.lang.IllegalStateException: Servlet response already use stream, Writer not possible
     at org.ajax4jsf.webapp.FilterServletResponseWrapper.getWriter(FilterServletResponseWrapper.java:226)
and thanks in advance

[shane.bryzak]

You could implement it as a resource (by extending org.jboss.seam.web.AbstractResource).  Take a look at GraphicImageResource, Remoting or CaptchaImage for examples.

[tdsproule]

Thanks for the pointer Siarhei.  Exactly what I needed.

I got the HttpServletResponse through FacesContext - here is a code fragment that I ended up using:

public void downloadExtract() throws MobileSenseException, IOException {
          
     byte[] excelExtract;
          
     try {
          excelExtract = excelExportServices.CreateDownload(walletAccount,
                         getMinDateTime(), getMaxDateTime());
          
          HttpServletResponse response = (HttpServletResponse)FacesContext.getCurrentInstance().getExternalContext().getResponse();
          
          response.setContentType("application/octet-stream");
          response.addHeader("Content-Disposition","attachment;filename=" +
                         makeExtractFileName(getMinDateTime(),getMaxDateTime()));
               
          response.setContentLength(excelExtract.length);
               
          OutputStream writer = response.getOutputStream();
               
          writer.write(excelExtract);
               
          writer.flush();
          writer.close();
          
          FacesContext.getCurrentInstance().responseComplete();               
          
     } catch (ExtractEmptyException e) {
          facesMessages.add("There is nothing to export with the selected dates");
     } 
          
}

[bidance]

i mainly used the same source code but it didn t succeed i m using facelets as my view handler(declared in faces config) i used faces config the same way but i still get the above exception is there any workaround! using a seam AbstractResource may  prevent me from injecting parameters from the users input to generate the in memory excel file 

[shane.bryzak]

A Resource still provides access to the HttpServletRequest object, so you can still read any parameters that are passed in.