如何在 Angular 中自动检测内容类型

Question

In my Angular 9 application I am trying to automatically set the content-type for every different HTTP request I do.

In Angular doc I found this detectContentTypeHeader method but it seems not working good. In my case for example for this type of body:

{"username":"admin","password":"pwd","tenant":"12345"}

it detects text/plain instead of application/json but the body is a correct JSON, so am I wrong something? Is there a way to do it automatically or I need to set it for every request? (I am already using an interceptor)

multipart/form-data

Answer 1

If you pass in an object instead of a string as the request body it will detect it as application/json .

The reason it's detecting a string as text/plain is written in the source code

Technically, strings could be a form of JSON data, but it's safe enough to assume they're plain strings

If for some reason you still want to detect a string as a valid JSON you can do the following:

let contentType = req.detectContentTypeHeader();

if (typeof req.body === 'string') {
  try {
    JSON.parse(req.body);
    contentType = 'application/json';
  } catch {}
}

req = req.clone({ headers: req.headers.set('content-type', contentType) });