Timeout when generate excel for download - apache-poi

Question

I am trying to export Excel using poi and servlet. code like this
SXSSFWorkbook workbook = genrateExcel(id)
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
workbook.write(outputStream);
byte[] outArray = outputStream.toByteArray();
response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
response.setContentLength(outArray.length);
response.setHeader("Expires:", "0");
response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(excelFileName, "UTF-8"));
OutputStream outStream = response.getOutputStream();
outStream.write(outArray);
outStream.flush();
workbook.dispose();
workbook.close();
But sometimes generating costs too much time,so i get a 504 timeout error.
I wonder how can I hold the connection until file is generated ?
UPDATE:
thanks Gagravarr. I update the code to this
ExecutorService threadPool = Executors.newSingleThreadExecutor();
Future<SXSSFWorkbook> future = threadPool.submit(new Callable<SXSSFWorkbook>() {
#Override
public SXSSFWorkbook call() {
return genrateExcel(id);
}
});
SXSSFWorkbook workbook = null;
try {
response.setHeader("Expires:", "0");
response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(excelFileName, "UTF-8"));
response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
OutputStream outStream = response.getOutputStream();
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
int times = 0;
while (times < 50) {
if (future.isDone()) {
workbook = future.get();
break;
}
outStream.flush();
Thread.sleep(5000);
times++;
}
workbook = workbook == null ? new SXSSFWorkbook() : workbook;
workbook.write(outputStream);
byte[] outArray = outputStream.toByteArray();
response.setContentLength(outArray.length);
outStream.write(outArray);
outStream.flush();
workbook.dispose();
workbook.close();
} catch (Exception e) {
e.printStackTrace();
}
But got a ClientAbortException: java.io.IOException meanwhile Chrome report the page isnot working ERR_INCOMPLETE_CHUNKED_ENCODING is sth wrong?