Spring mvc upload multiple files at once with AJAX doesn't work - ajax

Question

I'm using Spring boot 2.0.1 and I'm trying to upload multiple files with dropzone. Everything is working perfectly when I'm using uploadMultiple: false on Dropzone.js. When I set uploadMultiple: true, My Controller stops working.
The controller class is as follow:
#PostMapping(value = "/img/upload")
public ResponseEntity<?> fileUpload(#RequestParam("file") MultipartFile[] files){
System.out.println(files.length);
for (MultipartFile file : files) {
try {
file.transferTo(new File("/opt/img/" + file.getOriginalFilename()));
System.out.println(file.getOriginalFilename());
} catch (IOException e) {
e.printStackTrace();
}
}
return new ResponseEntity<>("File Uploaded Successfully.", HttpStatus.OK);
}
The files are no more than 1MB and my settings are
spring.servlet.multipart.max-file-size=10MB
spring.servlet.multipart.max-request-size=10MB
My request header when I upload the files:
------WebKitFormBoundaryihPcX9WHR5UA9jGD
Content-Disposition: form-data; name="file[0]"; filename="cars-02-01.png"
Content-Type: image/png
------WebKitFormBoundaryihPcX9WHR5UA9jGD
Content-Disposition: form-data; name="file[1]"; filename="Screenshot from 2018-05-03 23-31-53.jpg"
Content-Type: image/jpeg
Everything seems perfect. I still cannot find the reason for this problem?

Answer 1

It seems that I should use the MultipartHttpServletRequest instead of MultipartFile[] files. I Changed the method to:
#PostMapping(value = "/img/upload")
public ResponseEntity<?> fileUpload(MultipartHttpServletRequest request) {
Map<String, MultipartFile> fileMap = request.getFileMap();
for (MultipartFile file : fileMap.values()) {
try {
file.transferTo(new File("/opt/img/" + file.getOriginalFilename()));
System.out.println(file.getOriginalFilename());
} catch (IOException e) {
e.printStackTrace();
}
}
return new ResponseEntity<>("File Uploaded Successfully.", HttpStatus.OK);
}