Returning excel file using spring boot controller - excel

Question

I was trying to make a rest endpoint in Spring Boot which reads from DB, generates an excel file(Using Apache POI) which is returned to the user using HttpServletResponse but when I invoke this, the excel is getting created but it's not downloading. I had some other code earlier in place which was working fine but I accidentally removed that and now I'm stuck. Any help/leads are appreciated.
#RequestMapping(path = "/save", method = RequestMethod.GET)
public ResponseEntity<String> saveToXls(#RequestParam String id, #RequestParam String appName, HttpServletResponse response) {
AppInstance appInstance = appInstanceRepo.get(id);
List<DownloadDetail> downloadDetailList = downloadDAO.searchByInstanceId(id);
//List<DownloadDetail> downloadDetailList = appInstance.getDownloads();
System.out.print("LIST SIZE:" + downloadDetailList.size());
String fileName = appName + " report";
File myFile = new File(fileName + ".xls");
FileOutputStream fileOut;
downloadDetailList.forEach(downloadDetail -> System.out.print(downloadDetail.getSid()));
try {
try (HSSFWorkbook workbook = new HSSFWorkbook()) {
HSSFSheet sheet = workbook.createSheet("lawix10");
HSSFRow rowhead = sheet.createRow((short) 0);
rowhead.createCell((short) 0).setCellValue("SID");
rowhead.createCell((short) 1).setCellValue("Download Time");
rowhead.createCell((short) 2).setCellValue("OS Version");
int i = 0;
for (DownloadDetail downloadDetail : downloadDetailList) {
System.out.print("In loop -2");
HSSFRow row = sheet.createRow((short) i);
row.createCell((short) 0).setCellValue(downloadDetail.getSid());
row.createCell((short) 1).setCellValue(downloadDetail.getDownloadTime());
row.createCell((short) 2).setCellValue(downloadDetail.getOsVersion());
i++;
}
fileOut = new FileOutputStream(myFile);
workbook.write(fileOut);
}
fileOut.close();
byte[] buffer = new byte[10240];
response.addHeader("Content-disposition", "attachment; filename=test.xls");
response.setContentType("application/vnd.ms-excel");
try (
InputStream input = new FileInputStream(myFile);
OutputStream output = response.getOutputStream();
) {
for (int length = 0; (length = input.read(buffer)) > 0;) {
output.write(buffer, 0, length);
}
}
response.flushBuffer();
} catch (FileNotFoundException e1) {
e1.printStackTrace();
} catch (IOException e1) {
e1.printStackTrace();
}
return null;
}
EDIT:
I tried to do it another way as shown below:
try (InputStream is = new FileInputStream(myFile)) {
response.addHeader("Content-disposition", "attachment; filename=test.xls");
response.setContentType("application/vnd.ms-excel");
IOUtils.copy(is, response.getOutputStream());
}
response.flushBuffer();
This also doesn't seem to cut it.

Answer 1

This is a my example. Probably the issue is how you manage the OutputStream:
ServletOutputStream os = response.getOutputStream();
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-Disposition", "attachment; filename=\""+fileName+".xls\"");
workbook = excelStrategyMap.get(strategy).export(idList, status, params);
workbook.write(os);
workbook.close();
os.flush();
response.flushBuffer();

Answer 2

Once you get the workbook file, set the file name and file type. and add the response header and content type as mentioned below.
Then write the file to the response and flush it's buffer.
XSSFWorkbook file = excelUploadService.downloadDocument();
String filename = "Export.xlsx";
String filetype = "xlsx";
response.addHeader("Content-disposition", "attachment;filename=" + filename);
response.setContentType(filetype);
// Copy the stream to the response's output stream.
file.write(response.getOutputStream());
response.flushBuffer();
In the client side, get the response from the REST API and set the content type received by the response object. Using FileSaver library save the file into your local file system.
Here is the documentation for FileSaver js -- File saver JS Library
var type = response.headers("Content-Type");
var blob = new Blob([response.data], {type: type});
saveAs(blob, 'Export Data'+ '.xlsx');

Answer 3

#GetMapping(value = "/", produces = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
#ResponseBody
public byte[] generateExcel() {
byte[] res = statisticsService.generateExcel();
return res;