FormData 如何在 multipart/form-data - Angular 中获取或设置边界

Question

我有一个迷你应用程序，我必须在其中 post 从浏览器向端点发送表单数据。

这是我的 post:

var formData = new FormData();
formData.append('blobImage', blob, 'imagem' + (new Date()).getTime());

return $http({
  method: 'POST',
  url: api + '/url',
  data: formData,
  headers: {'Content-Type': 'multipart/form-data'}
})

边界似乎是由 formData 添加到参数中的，但是，我无法将其发送到 header，我该怎么办？

Answer 1

嗯，似乎 headers ContentType 应该是未定义的，以便添加正确的边界

Answer 2

正确的方法是不设置 Content-Type header.

示例：

import { http } from '@angular/common/http'

function sendPostData(form: FormData) {
  const url = `https://post-url-example.com/submit`;
  const options = {
    headers: new HttpHeaders({
      Authorization: `Bearer auth-token`
    })
  };

  return http.post(url, form, options);
}

进一步添加Pablo's answer.

当 http 请求 body 具有 FormData 类型时，angular 将延迟 Content-Type header 分配给浏览器。 detectContentTypeHeader() 将 return null FormData 请求 body 并且 angular 不会设置请求 header.

这是在 @angular/commons/http/src/xhr.ts 模块上。

  // Auto-detect the Content-Type header if one isn't present already.
  if (!req.headers.has('Content-Type')) {
    const detectedType = req.detectContentTypeHeader();
    // Sometimes Content-Type detection fails.
    if (detectedType !== null) {
      xhr.setRequestHeader('Content-Type', detectedType);
    }
  }

Content-Type 根据请求检测 body:

  detectContentTypeHeader(): string|null {
    // An empty body has no content type.
    if (this.body === null) {
      return null;
    }
    // FormData bodies rely on the browser's content type assignment.
    if (isFormData(this.body)) {
      return null;
    }
    // Blobs usually have their own content type. If it doesn't, then
    // no type can be inferred.
    if (isBlob(this.body)) {
      return this.body.type || null;
    }
    // Array buffers have unknown contents and thus no type can be inferred.
    if (isArrayBuffer(this.body)) {
      return null;
    }
    // Technically, strings could be a form of JSON data, but it's safe enough
    // to assume they're plain strings.
    if (typeof this.body === 'string') {
      return 'text/plain';
    }
    // `HttpUrlEncodedParams` has its own content-type.
    if (this.body instanceof HttpParams) {
      return 'application/x-www-form-urlencoded;charset=UTF-8';
    }
    // Arrays, objects, and numbers will be encoded as JSON.
    if (typeof this.body === 'object' || typeof this.body === 'number' ||
        Array.isArray(this.body)) {
      return 'application/json';
    }
    // No type could be inferred.
    return null;
  }

来源：

FormData 如何在 multipart/form-data - Angular 中获取或设置边界

FormData how to get or set boundary in multipart/form-data - Angular

javascript

multipartform-data

angularjs