java - Create file .xls -

i want create file. xls in java, not want him stored anywhere. want created , presented download.

i have following code, after downloading excel file says file not valid.

private void criarficheirodeexemplo(requestcontext requestcontext) throws ioexception, interruptedexception {        requestcontext.sresponse.setcontenttype("excel.application");     requestcontext.sresponse.setheader("content-disposition", "attachment; filename =ficheiro_de_exemplo_incidencias.xls");      java.io.printwriter pw = requestcontext.sresponse.getwriter();      string ficheiro = construirformatoficheirodeexemplo();     pw.println(ficheiro);      pw.flush();     thread.sleep(2000);     pw.close(); }  private string construirformatoficheirodeexemplo() {     stringbuffer html = new stringbuffer();     html.append("<table>"); //"cria" tabela     html.append("<tr>");     html.append("<td>");     html.append("<strong>id_incidencia</strong>");     html.append("</td>");     html.append("</tr>"); //"cria" uma linha e uma coluna     html.append("</table>");         return html.tostring(); } 

any suggestions?

save file disk , open in text editor see if contains expect. if does, , excel won't open it, problem isn't download process. problem what's in file.

if don't want mess around generating excel-format binary data, , don't need formulas in spreadsheet, can excel open tsv or csv format (which plain text).