Adding a HTTP header to the Angular HttpClient doesn't send the header, why?

Here is my code:

import { HttpClient, HttpErrorResponse, HttpHeaders } from '@angular/common/http';

---

logIn(username: string, password: string) {
    const url = 'http://server.com/index.php';
    const body = JSON.stringify({username: username,
                                 password: password});
    const headers = new HttpHeaders();
    headers.set('Content-Type', 'application/json; charset=utf-8');
    this.http.post(url, body, {headers: headers}).subscribe(
        (data) => {
            console.log(data);
        },
        (err: HttpErrorResponse) => {
            if (err.error instanceof Error) {
                console.log('Client-side error occured.');
            } else {
                console.log('Server-side error occured.');
            }
        }
    );
}

and here the network debug:

Request Method:POST
Status Code:200 OK
Accept:application/json, text/plain, */*
Accept-Encoding:gzip, deflate
Accept-Language:en-US,en;q=0.8
Cache-Control:no-cache
Connection:keep-alive
Content-Length:46
Content-Type:text/plain

and Data are stored in 'Request Payload' but in my server doesn't received the POST values:

print_r($_POST);
Array
(
)

I believe the error comes from the header not set during the POST, what did I do wrong?

The instances of the new HttpHeader class are immutable objects. Invoking class methods will return a new instance as result. So basically, you need to do the following:

let headers = new HttpHeaders();
headers = headers.set('Content-Type', 'application/json; charset=utf-8');

or

const headers = new HttpHeaders({'Content-Type':'application/json; charset=utf-8'});

Update: adding multiple headers

let headers = new HttpHeaders();
headers = headers.set('h1', 'v1').set('h2','v2');

or

const headers = new HttpHeaders({'h1':'v1','h2':'v2'});

Update: accept object map for HttpClient headers & params

Since 5.0.0-beta.6 is now possible to skip the creation of a HttpHeaders object an directly pass an object map as argument. So now its possible to do the following:

http.get('someurl',{
   headers: {'header1':'value1','header2':'value2'}
});

To add multiples params or headers you can do the following:

constructor(private _http: HttpClient) {}

//....

const url = `${environment.APP_API}/api/request`;

let headers = new HttpHeaders().set('header1', hvalue1); // create header object
headers = headers.append('header2', hvalue2); // add a new header, creating a new object
headers = headers.append('header3', hvalue3); // add another header

let params = new HttpParams().set('param1', value1); // create params object
params = params.append('param2', value2); // add a new param, creating a new object
params = params.append('param3', value3); // add another param 

return this._http.get<any[]>(url, { headers: headers, params: params })

set http headers like below in your http request

return this.http.get(url, { headers: new HttpHeaders({'Authorization': 'Bearer ' + token})
 });

I struggled with this for a long time. I am using Angular 6 and I found that

let headers = new HttpHeaders();
headers = headers.append('key', 'value');

did not work. But what did work was

let headers = new HttpHeaders().append('key', 'value');

did, which makes sense when you realize they are immutable. So having created a header you can't add to it. I haven't tried it, but I suspect

let headers = new HttpHeaders();
let headers1 = headers.append('key', 'value');

would work too.

I was with Angular 8 and the only thing which worked for me was this:

  getCustomHeaders(): HttpHeaders {
    const headers = new HttpHeaders()
      .set('Content-Type', 'application/json')
      .set('Api-Key', 'xxx');
    return headers;
  }

In the manual (https://angular.io/guide/http) I read: The HttpHeaders class is immutable, so every set() returns a new instance and applies the changes.

The following code works for me with angular-4:

return this.http.get(url, {headers: new HttpHeaders().set('UserEmail', email ) });

First, you need to add HttpHeaders with HttpClient

import { HttpClient,HttpHeaders  } from '@angular/common/http';

your constructor should be like this.

constructor(private http: HttpClient) { }

then you can use like this

   let header = new HttpHeaders({ "Authorization": "Bearer "+token});

   const requestOptions = {  headers: header};                                                                                                                                                                            

    return this.http.get<any>(url, requestOptions)
        .toPromise()
        .then(data=> {
            //...
            return data;
    });

In my legacy app Array.from of prototype js was conflicting with angular's Array.from that was causing this problem. I resolved it by saving angular's Array.from version and reassigning it after prototype load.

I was struggling with this as well. I used an interceptor, it captures the response headers, then clone the headers(since headers are immutable objects) and then sends the modified headers. https://angular.io/guide/http#intercepting-requests-and-responses

Angular 8 HttpClient Service example with Error Handling and Custom Header

	import { Injectable } from '@angular/core';
	import { HttpClient, HttpHeaders, HttpErrorResponse } from '@angular/common/http';
	import { Student } from '../model/student';
	import { Observable, throwError } from 'rxjs';
	import { retry, catchError } from 'rxjs/operators';

	@Injectable({
	  providedIn: 'root'
	})
	export class ApiService {

	  // API path
	  base_path = 'http://localhost:3000/students';

	  constructor(private http: HttpClient) { }

	  // Http Options
	  httpOptions = {
		headers: new HttpHeaders({
		  'Content-Type': 'application/json'
		})
	  }

	  // Handle API errors
	  handleError(error: HttpErrorResponse) {
		if (error.error instanceof ErrorEvent) {
		  // A client-side or network error occurred. Handle it accordingly.
		  console.error('An error occurred:', error.error.message);
		} else {
		  // The backend returned an unsuccessful response code.
		  // The response body may contain clues as to what went wrong,
		  console.error(
			`Backend returned code ${error.status}, ` +
			`body was: ${error.error}`);
		}
		// return an observable with a user-facing error message
		return throwError(
		  'Something bad happened; please try again later.');
	  };


	  // Create a new item
	  createItem(item): Observable<Student> {
		return this.http
		  .post<Student>(this.base_path, JSON.stringify(item), this.httpOptions)
		  .pipe(
			retry(2),
			catchError(this.handleError)
		  )
	  }
	  
	  ....
	  ....

Check complete example tutorial here