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。

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));

下面的代码以最简单的形式在Angular 6/7中工作

this.http.post("http://destinationurl.com/endpoint", fileFormData)
  .subscribe(response => {
    //handle response
  }, err => {
    //handle error
  });

下面是完整的实现

jspdf和Angular 8

我生成了一个pdf，并希望通过POST请求上传pdf，这就是我所做的(为了清晰起见，我删除了一些代码和服务层)

import * as jsPDF from 'jspdf';
import { HttpClient } from '@angular/common/http';

constructor(private http: HttpClient)

upload() {
    const pdf = new jsPDF()
    const blob = pdf.output('blob')
    const formData = new FormData()
    formData.append('file', blob)
    this.http.post('http://your-hostname/api/upload', formData).subscribe()
}

根据上面的答案，我用Angular 5.x构建了这个

只需调用uploadFile(url, file).subscribe()来触发上传

import { Injectable } from '@angular/core';
import {HttpClient, HttpParams, HttpRequest, HttpEvent} from '@angular/common/http';
import {Observable} from "rxjs";

@Injectable()
export class UploadService {

  constructor(private http: HttpClient) { }

  // file from event.target.files[0]
  uploadFile(url: string, file: File): Observable<HttpEvent<any>> {

    let formData = new FormData();
    formData.append('upload', file);

    let params = new HttpParams();

    const options = {
      params: params,
      reportProgress: true,
    };

    const req = new HttpRequest('POST', url, formData, options);
    return this.http.request(req);
  }
}

在组件中像这样使用它

  // At the drag drop area
  // (drop)="onDropFile($event)"
  onDropFile(event: DragEvent) {
    event.preventDefault();
    this.uploadFile(event.dataTransfer.files);
  }

  // At the drag drop area
  // (dragover)="onDragOverFile($event)"
  onDragOverFile(event) {
    event.stopPropagation();
    event.preventDefault();
  }

  // At the file input element
  // (change)="selectFile($event)"
  selectFile(event) {
    this.uploadFile(event.target.files);
  }

  uploadFile(files: FileList) {
    if (files.length == 0) {
      console.log("No file selected!");
      return

    }
    let file: File = files[0];

    this.upload.uploadFile(this.appCfg.baseUrl + "/api/flash/upload", file)
      .subscribe(
        event => {
          if (event.type == HttpEventType.UploadProgress) {
            const percentDone = Math.round(100 * event.loaded / event.total);
            console.log(`File is ${percentDone}% loaded.`);
          } else if (event instanceof HttpResponse) {
            console.log('File is completely loaded!');
          }
        },
        (err) => {
          console.log("Upload Error:", err);
        }, () => {
          console.log("Upload done");
        }
      )
  }