Empty List<MultipartFile> when trying to upload many files in Spring with ng-file-upload

The problem was that ng-file-upload by default submits array of files using names file[0], file[1] etc. It is configurable with the arrayKey value when using Upload Service. Setting it to empty string forces the files to be sent under the same file key, which is correctly resolved with Spring and the @RequestParam("file") List<MultipartFile> contains all files that has been submitted.

Upload.upload({url: url, data: {file: arrayOfFiles}, arrayKey: ''})

Try to use @ModelAttribute like this:

    @RequestMapping(value = "/{user}/attachment", method = RequestMethod.POST)    @PreAuthorize(...)     public void upload(@PathVariable User user,@ModelAttribute("uploadFile") FileUpload uploadFile) throws IllegalStateException, IOException {    List<MultipartFile> files = uploadFile.getFiles();    ...

And create a class like:

     public class FileUpload {     private List<MultipartFile> files;     public List<MultipartFile> getFiles() {        return files;     }    public void setFiles(List<MultipartFile> files) {       this.files= files;      }   }

That works for me, sending big 'email' object with multiple file attachments from UI to back-end:

Angular

sendEmailWithAttachments(taskId: string, template: string, email: any, modelConfig: any, files: any[]) {    let formData = new FormData();    formData.append('form', new Blob([JSON.stringify(email)], {type: 'application/json'}));    files.forEach(file  => {        formData.append('files', file);    });    return this.$http({        method: 'POST',        data: formData,        url: this.baseUrl + '/' + taskId + '/email-with-attachment?template=' + template,        headers: {            'Content-Type': undefined        },        responseType: 'arraybuffer'    });}

Java Spring

@RequestMapping(value = "{taskId}/email-with-attachment", method = RequestMethod.POST, consumes = MULTIPART_FORM_DATA_VALUE)public void sendEmailWithAttachment(        @PathVariable String taskId,        @RequestParam String template,        @RequestParam("form") MultipartFile form,        @RequestParam("files") List<MultipartFile> files) throws IOException {    Map<String, String> parameters = new ObjectMapper().readValue(form.getInputStream(), HashMap.class);        System.out.println("taskId"+ taskId);    System.out.println("template"+ template);    System.out.println("files"+ files);    System.out.println("parameters"+ parameters);}