Angular interceptor, handle HTTP Error and retry

Question

I have a basic JWT system, and an Interceptor that checks whether the request fails due to being unauthorized.

import {Injectable} from '@angular/core';
import {HttpErrorResponse, HttpEvent, HttpHandler, HttpInterceptor, HttpRequest} from '@angular/common/http';
import {Observable, throwError} from 'rxjs';
import {AuthService} from '../services/auth.service';
import {catchError, retryWhen} from 'rxjs/operators';

@Injectable()
export class AuthenticationErrorInterceptor implements HttpInterceptor {

  private readonly _authService: AuthService;

  constructor(authService: AuthService) {
    this._authService = authService;
  }

  public intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const authReq = req.clone({headers: req.headers});
    return next.handle(authReq)
      .pipe(
        catchError((err) => this._handleAuthError(err)),
        retry(3)
      );
  }

  private _handleAuthError(error: HttpErrorResponse): Observable<any> {
    if (error.status === 401 || error.status === 403) {
      return this._authService.authenticate();
    }

    return throwError(error);
  }
}

If the request does fail then I want to resend the request after I have called this._authService.authenticate();. It will reauthenticate, due to the error handling forcing it to reauthenticate but then it doesn't recall the request causing the app to fail until I refresh the browser.

How can I get my guard to try the request again?

I've tried using retryWhen as well but I get the same/similar result.

Answer 1

Call .next on the HTTP handler after you have re-authenticated your session. Ideally, you should return an authentication token from your authenticate method that can then be appended onto the request auth headers.

import {Injectable} from '@angular/core';
import {HttpErrorResponse, HttpEvent, HttpHandler, HttpInterceptor, HttpRequest} from '@angular/common/http';
import {Observable, throwError} from 'rxjs';
import {AuthService} from '../services/auth.service';
import {catchError, retryWhen} from 'rxjs/operators';

@Injectable()
export class AuthenticationErrorInterceptor implements HttpInterceptor {

  private readonly _authService: AuthService;

  constructor(authService: AuthService) {
    this._authService = authService;
  }

  public intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
      return next.handle(req)
            .pipe(
                catchError((error: HttpErrorResponse) => {
                  if (error.status === 401 || error.status === 403) {
                    return this._authService.authenticate()
                      .pipe(
                        mergeMap((token) => next.handle(req.clone({
                                    headers: req.headers.set(AUTH_TOKEN_NAME_HERE, token)
                                })))
                      );
                  }

                    return throwError(error);
                })
            );
  }
}