Example of Http Interceptor for login authentication

Example of Http Interceptor for login authentication

An Http Interceptor can be used to verify if the user is logged in or to inject http headers to every http request.

In the example above, we are injecting a Authorization http header to every request:

auth-interceptor.js

import { Injectable, Injector } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler, HttpEvent } from '@angular/common/http';
import { Observable } from 'rxjs/Observable';
import { LoginService } from './login.service';
 
@Injectable()
export class AuthInterceptor implements HttpInterceptor {
 
  constructor(private injector: Injector) {
 
  }
 
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const loginService = this.injector.get(LoginService);
 
    if (loginService.isLoggedIn()) {
      const authRequest = request.clone(
        { setHeaders:{'Authorization': `Bearer ${loginService.getUser().accessToken}`}});
 
      return next.handle(authRequest);
    } else {
      return next.handle(request);
    }
  }
}

In your module:

import { HTTP_INTERCEPTORS, HttpClientModule } from '@angular/common/http';
import { AuthInterceptor } from "./login/auth.interceptor";
 
@NgModule({
  ...
  providers: [
    ...
    {
      provide: HTTP_INTERCEPTORS,
      useClass: AuthInterceptor,
      multi: true
    },
    ...
  ]
  ...
})