Trying to send Http response to the frontend before method logic happens - spring-boot

Question

What I am trying to accomplish is I have a controller that gets accessed from a frontend (Angular). The users uploads an array of images from the frontend and those images are sent and processed through the backend (Spring Boot). Before the images are processed, I would like to send a response (200) to the frontend so the user does not have to wait for the images to be processed. The code looks like so:
#CrossOrigin
#RestController
public class SolarController {
#Autowired
SolarImageServiceImpl solarImageService;
#Autowired
SolarVideoServiceImpl solarVideoService;
#ApiOperation(value = "Submit images")
#PostMapping(value="/solarImage", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public void getUploadImages(#ApiParam(value = "Upload images", required = true) #RequestPart(value = "files") MultipartFile[] files,
#ApiParam(value = "User's LanId", required = true) #RequestParam(value = "lanID") String lanId,
#ApiParam(value = "Site name", required = true) #RequestParam(value = "siteName") String siteName,
#ApiParam(value = "User email", required = true) #RequestParam(value = "userEmail") String userEmail,
#ApiParam(value = "Inspection ID", required = true) #RequestParam(value = "inspectionID") String inspectionID) throws IOException{
if (!ArrayUtils.isEmpty(files)) {
this.solarImageService.uploadImages(files, lanId, siteName, userEmail, inspectionID);
}
I have looked at multiple other examples, as in using #Async over the method, using HttpServletResponse, and setting my own responses. But nothing is working.

Answer 1

Resolved.
#ApiOperation(value = "Submit images")
#PostMapping(value="/solarImage", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
public void getUploadImages(#ApiParam(value = "Upload images", required = true) #RequestPart(value = "files") MultipartFile[] files,
#ApiParam(value = "User's LanId", required = true) #RequestParam(value = "lanID") String lanId,
#ApiParam(value = "Site name", required = true) #RequestParam(value = "siteName") String siteName,
#ApiParam(value = "User email", required = true) #RequestParam(value = "userEmail") String userEmail,
#ApiParam(value = "Inspection ID", required = true) #RequestParam(value = "inspectionID") String inspectionID, HttpServletResponse response) throws IOException{
int code = (!ArrayUtils.isEmpty(files)) ? HttpServletResponse.SC_OK
: HttpServletResponse.SC_NOT_FOUND;
if (code != HttpServletResponse.SC_OK) {
response.sendError(code);
return;
}
PrintWriter wr = response.getWriter();
response.setStatus(code);
wr.flush();
wr.close();
if (!ArrayUtils.isEmpty(files)) {
this.solarImageService.uploadImages(files, lanId, siteName, userEmail, inspectionID);
}
Sending the HttpServletResponse first did the trick. Annotating the method with #Async did not work.