Intercepting HTTP Requests to Include User Credentials in Angular

When sending a request to the server and the resource you are trying to access requires authorization, you would need to send a valid access token having the right permissions for the resource. If you use cookie authentication, you would need to pass a withCredentials = true to the options of the request in order to include the access token.

A sample get request would be:

this.http.get<string>(this.baseUrl + '/message/getMessage', { withCredentials: true }).subscribe((message: string) => { alert(message); });

We know that in every request, we would need to add withCredentials parameter; so, is there a way for us to automatically add this parameter when we invoke get or post? Fortunately, there is – using HttpInterceptor.

As the name suggests, an HttpInterceptor will intercept an HTTP request or response and execute certain lines of code before finally sending the request or process a response. HttpInterceptor would be very helpful for our case where we wanted to add withCredentials parameter on every request.

Create a class called AuthCredentialInterceptor with the following definition:

import { Injectable } from '@angular/core';
import { HttpEvent, HttpInterceptor, HttpHandler, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()
export class AuthCredentialInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const authReq = req.clone({
      withCredentials: true
    });

    return next.handle(authReq);
  }
}

Our interceptor has a simple logic – clone our request, add a withCredentials parameter and process the cloned request.

Then, you would have to tell our app module to use this interceptor on every request:

import { HTTP_INTERCEPTORS } from '@angular/common/http';
import { AuthCredentialInterceptor } from './@core/http/auth.interceptor';

@NgModule({
  // other attributes here
  providers: [
    {
      provide: HTTP_INTERCEPTORS, useClass: AuthCredentialInterceptor, multi: true
    }
  ],
  bootstrap: [AppComponent]
})
export class AppModule { }

Now, we can rewrite our original request without the need to specify the withCredentials parameter:

this.http.get<string>(this.baseUrl + '/message/getMessage').subscribe((message: string) => { alert(message); });

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