How to download an excel file in Spring RestController

I am using Apache POI to generate .xlsx file.

I would like to return that file from Spring controller. Here’s what I’ve done so far:

Controller:

@RequestMapping(method = RequestMethod.GET)
    public HttpEntity<byte[]> createExcelWithTaskConfigurations(HttpServletResponse response) throws IOException {
        byte[] excelContent = excelService.createExcel();

        HttpHeaders header = new HttpHeaders();
        header.setContentType(new MediaType("application", "vnd.openxmlformats-officedocument.spreadsheetml.sheet"));
        header.set(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=my_file.xls");
        header.setContentLength(excelContent.length);

        return new HttpEntity<>(excelContent, header);
    }

Is it possible to return actual excel file from rest controller so user can download it to his computer ? As for now controller returning byte[] but I would like to return it actual file. How can I achieve that ?

Answer

You can use ByteArrayResource to download as a file. Below is the modified code snippet of yours

    @GetMapping(value="/downloadTemplate")
    public HttpEntity<ByteArrayResource> createExcelWithTaskConfigurations() throws IOException {
        byte[] excelContent = excelService.createExcel();

        HttpHeaders header = new HttpHeaders();
        header.setContentType(new MediaType("application", "force-download"));
        header.set(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=my_file.xlsx");


        return new HttpEntity<>(new ByteArrayResource(excelContent), header);
    }

If you are trying to generate excel using apache poi, please find the code snippet below

    @GetMapping(value="/downloadTemplate")
    public ResponseEntity<ByteArrayResource> downloadTemplate() throws Exception {
        try {
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            XSSFWorkbook workbook = createWorkBook(); // creates the workbook
            HttpHeaders header = new HttpHeaders();
            header.setContentType(new MediaType("application", "force-download"));
            header.set(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=ProductTemplate.xlsx");
            workbook.write(stream);
            workbook.close();
            return new ResponseEntity<>(new ByteArrayResource(stream.toByteArray()),
                    header, HttpStatus.CREATED);
        } catch (Exception e) {
            log.error(e.getMessage());
            return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
        }
    }