ajax and spring mvc to download file - ajax

Question

My task is to download file on button click. Data in file should be fetched from Service. I did this approach in three steps:
1) Ajax call to first controller. In this controoler: create file, call service, get data from service, write to file AND return fileName to AJAX success() callback.
2) Using a response from first request (file name), I'm doing this:
window.location.href = 'downloadFile/' + response;
to call second controller that will download the file.
This approach perfectly works on my local computer.
My problem is, it makes two requests and each time the request will be made to different hosts (in prod). So it will not find the file in second controller.
So I cannot call controller two times. When I try to combine these two methods together in one controller method - it's not starting download a file.
Why it happens? Why it's starting download only if I return file name to success() callback and then call second controller method again that will write the file to HtttpServletResponse.?
$.ajax({
type : "GET",
contentType : "application/json",
url : "createFile",
dataType : 'text',
success : function(response) {
console.log(response);
window.location.href = 'downloadFile/' + response;
}
}); <%--end of AJAX call--%>
#RequestMapping(value = "/createFile", method = RequestMethod.GET)
#ResponseStatus(value=HttpStatus.OK)
#ResponseBody String createFile(#RequestParam("startDate") String startDate,
#RequestParam("endDate") String endDate,
#RequestParam("vendorId") String vendorId, HttpServletResponse httpResponse) throws Exception {
File file = new File("mynewfile.csv");
BufferedWriter writer = new BufferedWriter(new FileWriter(file));
List<Data> dataFromService = getDataFromService();
httpResponse.setHeader("Content-Disposition", "attachment; filename=\"" + "mynewfile" + ".csv\"");
httpResponse.setContentType("application/csv");
for (int i = 0; i < dataFromService.size(); i++) {
Data data = dataFromService.get(i);
writer.write(data.getVendorName() + ", "
+ data.getAsin() + ", "
+ data.getReferenceId() + ", "
+ data.getCompleteCount() + "\n");
}
writer.close();
return file.GetName();
}
#RequestMapping(value = "/downloadFile/{file}", method = RequestMethod.GET)
public void downloadFile(File metricsReportFile, HttpServletResponse response) throws Exception {
File metricsReportFile = new File (file);
InputStream is = new FileInputStream(metricsReportFile);
response.setHeader("Content-Disposition", "attachment; filename=" + metricsReportFile.getName() );
FileCopyUtils.copy(is, response.getOutputStream());
response.flushBuffer();
metricsReportFile.delete();
}

Answer 1

You said that in production doesn't work. Is there a Cluster of servers or something? Maybe the request of the file creation is attended by an instance and when you try to get the file, another one is responding