以Angular 2发送文件

Question

以下是我的代码，我基本上是尝试使用我的应用程序发送csv和xlxs文件。虽然，一切看起来都对我来说，我仍然无法处理并将文件发送到我的后端。当我将文件发送到后端时，我从后端收到响应，因为＆＃34;没有上传文件＆＃34;虽然它使用邮差很好。我在代码中遗漏了什么？

文件组件

export class FileUploadComponent {
    constructor(private service:FileUploadService) {
        this.service.progress$.subscribe(
            data => {
                console.log('progress = '+data);
            });
    }

    onChange(event) {
        console.log('onChange');
         let files = event.target.files;
        console.log(files);
        this.service.makeFileRequest('http://localhost:9000/api/v1/fileUpload/country', [], files).subscribe(() => {
            console.log('sent');
        });
    }
}

的FileService

export class FileUploadService {
   public progress$;
   public progressObserver;
   public progress : number;


    constructor (private auth:AuthenticationService) {
        this.progress$ = Observable.create(observer => {
            this.progressObserver = observer
        }).share();
    }

     makeFileRequest (url: string, params: string[], files: File[]) {
        return Observable.create(observer => {
            let formData: FormData = new FormData(),
                xhr: XMLHttpRequest = new XMLHttpRequest();

            for (let i = 0; i < files.length; i++) {
                formData.append('uploads', files[i], files[i].name);

            }

            xhr.onreadystatechange = () => {
                if (xhr.readyState === 4) {
                    if (xhr.status === 200) {
                        observer.next(JSON.parse(xhr.response));
                        observer.complete();
                    } else {
                        observer.error(xhr.response);
                    }
                }
            };

            xhr.upload.onprogress = (event) => {

                this.progress = Math.round(event.loaded / event.total * 100);
                this.progressObserver.next(this.progress);
            };

            xhr.open('POST', url, true);
            xhr.setRequestHeader('Authorization', 'Bearer ' + this.auth.token);

            xhr.send(formData);


        });
    }

}