Hi Chris,
Please use "application/vnd.ms-excel" or "application/vnd.ms-workbook" mime type instead of "application/download".
See following codes (which are used to set response header in the demos):
private void setResponseHeader(HttpServletResponse response, String resultXLS)
{
response.setContentType("application/vnd.ms-excel");
response.addHeader("content-disposition", "inline; filename=" + resultXLS);
}