感谢@Eswar。这段代码非常适合我。我想在解决方案中添加一些东西:

我得到错误:java.io.IOException: RESTEASY007550:无法获得多部分的边界

为了解决这个错误，你应该删除“Content-Type”“multipart/form-data”。它解决了我的问题。

Angular 2对上传文件提供了很好的支持。不需要第三方库。

<input type="file" (change)="fileChange($event)" placeholder="Upload file" accept=".pdf,.doc,.docx">

fileChange(event) {
    let fileList: FileList = event.target.files;
    if(fileList.length > 0) {
        let file: File = fileList[0];
        let formData:FormData = new FormData();
        formData.append('uploadFile', file, file.name);
        let headers = new Headers();
        /** In Angular 5, including the header Content-Type can invalidate your request */
        headers.append('Content-Type', 'multipart/form-data');
        headers.append('Accept', 'application/json');
        let options = new RequestOptions({ headers: headers });
        this.http.post(`${this.apiEndPoint}`, formData, options)
            .map(res => res.json())
            .catch(error => Observable.throw(error))
            .subscribe(
                data => console.log('success'),
                error => console.log(error)
            )
    }
}

使用@angular/core": "~2.0.0"和@angular/http: "~2.0.0"

这是一个有用的教程，如何使用ng2-file-upload和不使用ng2-file-upload上传文件。

对我来说很有帮助。

目前，教程包含几个错误:

1-客户端应具有与服务器相同的上传url 在app.component.ts中更改行

const URL = 'http://localhost:8000/api/upload';

to

const URL = 'http://localhost:3000';

2-服务器发送响应为'text/html'，所以在app.component.ts更改

.post(URL, formData).map((res:Response) => res.json()).subscribe(
  //map the success function and alert the response
  (success) => {
    alert(success._body);
  },
  (error) => alert(error))

来

.post(URL, formData)  
.subscribe((success) => alert('success'), (error) => alert(error));

我已经成功地使用了下面的工具。我和primeNg没有利害关系，只是传递我的建议。

http://www.primefaces.org/primeng/#/fileupload

这个简单的解决方案对我很有效:file-upload.component.html

<div>
  <input type="file" #fileInput placeholder="Upload file..." />
  <button type="button" (click)="upload()">Upload</button>
</div>

然后在组件中直接使用XMLHttpRequest进行上传。

import { Component, OnInit, ViewChild } from '@angular/core';

@Component({
  selector: 'app-file-upload',
  templateUrl: './file-upload.component.html',
  styleUrls: ['./file-upload.component.css']
})
export class FileUploadComponent implements OnInit {

  @ViewChild('fileInput') fileInput;

  constructor() { }

  ngOnInit() {
  }

  private upload() {
    const fileBrowser = this.fileInput.nativeElement;
    if (fileBrowser.files && fileBrowser.files[0]) {
      const formData = new FormData();
      formData.append('files', fileBrowser.files[0]);
      const xhr = new XMLHttpRequest();
      xhr.open('POST', '/api/Data/UploadFiles', true);
      xhr.onload = function () {
        if (this['status'] === 200) {
            const responseText = this['responseText'];
            const files = JSON.parse(responseText);
            //todo: emit event
        } else {
          //todo: error handling
        }
      };
      xhr.send(formData);
    }
  }

}

如果使用dotnet core，参数名必须与from字段名匹配。本例中的文件:

[HttpPost("[action]")]
public async Task<IList<FileDto>> UploadFiles(List<IFormFile> files)
{
  return await _binaryService.UploadFilesAsync(files);
}

这个答案抄袭了http://blog.teamtreehouse.com/uploading-files-ajax

编辑: 上传后，您必须清除文件上传，以便用户可以选择一个新文件。与其使用XMLHttpRequest，不如使用fetch:

private addFileInput() {
    const fileInputParentNative = this.fileInputParent.nativeElement;
    const oldFileInput = fileInputParentNative.querySelector('input');
    const newFileInput = document.createElement('input');
    newFileInput.type = 'file';
    newFileInput.multiple = true;
    newFileInput.name = 'fileInput';
    const uploadfiles = this.uploadFiles.bind(this);
    newFileInput.onchange = uploadfiles;
    oldFileInput.parentNode.replaceChild(newFileInput, oldFileInput);
  }

  private uploadFiles() {
    this.onUploadStarted.emit();
    const fileInputParentNative = this.fileInputParent.nativeElement;
    const fileInput = fileInputParentNative.querySelector('input');
    if (fileInput.files && fileInput.files.length > 0) {
      const formData = new FormData();
      for (let i = 0; i < fileInput.files.length; i++) {
        formData.append('files', fileInput.files[i]);
      }

      const onUploaded = this.onUploaded;
      const onError = this.onError;
      const addFileInput = this.addFileInput.bind(this);
      fetch('/api/Data/UploadFiles', {
        credentials: 'include',
        method: 'POST',
        body: formData,
      }).then((response: any) => {
        if (response.status !== 200) {
          const error = `An error occured. Status: ${response.status}`;
          throw new Error(error);
        }
        return response.json();
      }).then(files => {
        onUploaded.emit(files);
        addFileInput();
      }).catch((error) => {
        onError.emit(error);
      });
    }

https://github.com/yonexbat/cran/blob/master/cranangularclient/src/app/file-upload/file-upload.component.ts

我已经上传文件使用引用。以这种方式上传文件不需要包。

//要写入.ts文件的代码

@ViewChild("fileInput") fileInput;

addFile(): void {
let fi = this.fileInput.nativeElement;
if (fi.files && fi.files[0]) {
  let fileToUpload = fi.files[0];
    this.admin.addQuestionApi(fileToUpload)
      .subscribe(
        success => {
          this.loading = false;
          this.flashMessagesService.show('Uploaded successfully', {
            classes: ['alert', 'alert-success'],
            timeout: 1000,
          });
        },
        error => {
          this.loading = false;
          if(error.statusCode==401) this.router.navigate(['']);
          else
            this.flashMessagesService.show(error.message, {
              classes: ['alert', 'alert-danger'],
              timeout: 1000,
            });
        });
  }

}

//服务中要编写的代码。ts文件

addQuestionApi(fileToUpload: any){
var headers = this.getHeadersForMultipart();
let input = new FormData();
input.append("file", fileToUpload);

return this.http.post(this.baseUrl+'addQuestions', input, {headers:headers})
      .map(response => response.json())
      .catch(this.errorHandler);

}

//用HTML编写的代码

<input type="file" #fileInput>