private void responseData(HSSFWorkbook wb) throws IOException {
  ByteArrayOutputStream baos = new ByteArrayOutputStream();
  wb.write(baos);
  baos.flush();
  byte[] aa = baos.toByteArray();
  excelStream = new ByteArrayInputStream(aa, 0, aa.length);
  baos.close();
}

<action name="exportXxx" class="xxxAction" method="exportXxx">
  <result name="exportSuccess" type="stream">
    <param name="inputName">excelStream</param>
    <param name="contentType">application/vnd.ms-excel</param>
    <param name="contentDisposition">attachment;filename="Undefined.xls"</param>
  </result>
</action>

@RequestMapping("/exportXxx.action")
public void exportXxx(HttpServletRequest request, HttpServletResponse response,
    @RequestParam(value="scheduleId", defaultValue="0")int scheduleId){
  HSSFWorkbook wb = createExcel(scheduleId) ;
  try {
    response.setHeader("Content-Disposition", "attachment; filename=appointmentUser.xls");
    response.setContentType("application/vnd.ms-excel; charset=utf-8") ;
    OutputStream out = response.getOutputStream() ;
    wb.write(out) ;
    out.flush();
    out.close();
  } catch (IOException e) {
    e.printStackTrace();
  } 
}