You were on the right track with response.getOutputStream(), but you're not using its output anywhere in your code. Essentially what you need to do is to stream the PDF file's bytes directly to the output stream and flush the response. In Spring you can do it like this:
@RequestMapping(value="/getpdf", method=RequestMethod.POST)
public ResponseEntity<byte[]> getPDF(@RequestBody String json) {
// convert JSON to Employee
Employee emp = convertSomehow(json);
// generate the file
PdfUtil.showHelp(emp);
// retrieve contents of "C:/tmp/report.pdf" that were written in showHelp
byte[] contents = (...);
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_PDF);
// Here you have to set the actual filename of your pdf
String filename = "output.pdf";
headers.setContentDispositionFormData(filename, filename);
headers.setCacheControl("must-revalidate, post-check=0, pre-check=0");
ResponseEntity<byte[]> response = new ResponseEntity<>(contents, headers, HttpStatus.OK);
return response;
}
Notes:
showHelp is not a good ideabyte[]: example hereshowHelp() to avoid overwriting the file if two users send a request at the same time