Interceptor not intercepting http requests (Angular 6)

Question

I\'m in the proces of adding an interceptor to my angular 6 project. To make calls to my API, I need to add a bearer token to all calls. Unfortunately the interceptor does n

Answer 1

In my case interceptor wasn't getting involved for service calls because I had imported HttpClientModule multiple times, for different modules.

Later I found that HttpClientModule must be imported only once. Doc ref

Hope this helps!

Answer 2

In my case i had a post method like this:

this.http.post<any>(this.authUrl, JSON.stringify({username: username, password: password})).pipe(
      map((response: any) => {
            let token: any = response.token;
            if (token) {
                localStorage.setItem('currentUser', 'value' }));                
                return response; 
            } else {
                return null;
            }
        }),
        catchError((error:any) => {return observableThrowError(error.json().error || 'Server error')})
      );

Because the map method could return null the interceptor stopt intercepting the requests made with this post method call. Don't ask me why this is so, but as soon as i replace null with say response everything started working again.

Answer 3

If you have a providers array for a module then you have to define the HTTP_INTERCEPTORS too for that module then only it will intercept the requests under that module.

e.g:

providers: [ 
// singleton services
PasswordVerifyService,
{ provide: HTTP_INTERCEPTORS, useClass: AppInterceptor, multi: true },
{ provide: HTTP_INTERCEPTORS, useClass: ErrorInterceptorService, multi: true }
]

Answer 4

You use the right way to intercept.

For people who use interceptor, you need to do 2 modifications :

Interceptor in service

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

import { Observable } from 'rxjs/Observable';
import 'rxjs/add/operator/do';

@Injectable()
export class MyInterceptor implements HttpInterceptor {
  intercept(
    req: HttpRequest<any>,
    next: HttpHandler
  ): Observable<HttpEvent<any>> {

    return next.handle(req).do(evt => {
      if (evt instanceof HttpResponse) {
        console.log('---> status:', evt.status);
        console.log('---> filter:', req.params.get('filter'));
      }
    });

  }
}

Provide HTTP_INTERCEPTOR

import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
(...)
  providers: [
    { provide: HTTP_INTERCEPTORS, useClass: MyInterceptor, multi: true }
  ],

Read this article for more details. It's pretty good

Answer 5

In my case, I had to import both HTTP_INTERCEPTORS, HttpClientModule in same module.