Question

I’m trying to get my JSF to export a spreadsheet for download. I’m using Apache’s POI library for the Excel document writing. I get the following error in an alert box when the code runs:

emptyResponse: An empty response was received from the server.

The method generating the spreadsheet and exporting to the OutputStream is below (I have renamed classes, methods etc for simplicity sake).

private void generateSpreadsheet(Object object) throws Exception {
    FacesContext context = FacesContext.getCurrentInstance();
    HttpServletResponse response = (HttpServletResponse)context.getExternalContext().getResponse();

    String fileName = object.getProperty() + ".xlsx";
    response.setContentType("application/vnd.ms-excel");
    response.setHeader("Content-Disposition", "attachment;filename=\"" + fileName +"\"");
    OutputStream os = response.getOutputStream();

    Workbook wb = new XSSFWorkbook();
    Sheet sheet = wb.createSheet("Sheet 1");
    Row row = sheet.createRow(0);
    Cell cell = row.createCell(0);
    cell.setCellValue("test");
    wb.write(os);

    os.flush();
    os.close();
    FacesContext.getCurrentInstance().responseComplete();
}

Any advice much appreciated, thanks.

Answer 1

If it makes a difference, I’m using AJAX (<f:ajax> tag) on the form submit that calls this method.

It makes definitely difference. You can not download files by Ajax. Ajax is executed by JavaScript code. But JavaScript has no facilities to force a Save As dialogue or to execute the platform default application associated with the file’s mime type (thankfully; that would have been a major security/intrusion problem). Further, the JSF Ajax API expects a XML response in a specified structure conform the JSF specs. When you send a complete Excel file instead, the whole Ajax response would be ignored as ununderstandable garbage by the JSF Ajax API.

You need to send a normal synchronous request. Remove the <f:ajax> tag from the command link/button. The current page will remain the same anyway if the download is sent as an attachment.