public String download() {
  ActionResponseImpl response = (ActionResponseImpl) FacesContext
    .getCurrentInstance().getExternalContext().getResponse();
  try {
   downloadFile(response,"","");
   return "";
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  // FacesContext.getCurrentInstance().responseComplete();
  return null;
}

public void downloadFile(ActionResponseImpl response, String realName,
   String fileName) throws IOException {
  System.out.println(response.getClass());
 
  response.getRealResponse().setHeader("Content-Disposition",
  "attachment; filename=b.rar");
  OutputStream output = response.getRealResponse().getOutputStream();
  byte[] b = new byte[1024];
  int i = 0;
  FileInputStream fis = new FileInputStream("c:/upload/upload2/b.rar");
  while ((i = fis.read(b)) > 0) {
   output.write(b, 0, i);
  }
  output.flush();
  output.close();
}

sorry,i speak  english is not very well,so i used google translation to send message to here.my project(jbossportal+jsf) has a problem.it is an download development,i can not download rar or doc file.it will be opened in IE.the problem is  "response.getRealResponse().setHeader()" can not do anything.please help me,thank you evenybody