Angular 4 Interceptor retry requests after token refresh

Question

Hi I am trying to figure out how implement the new angular interceptors and handle 401 unauthorized errors by refreshing the token and retrying the request. This is the guide I have been following: https://ryanchenkie.com/angular-authentication-using-the-http-client-and-http-interceptors

I am successfully caching the failed requests and can refresh the token but I cannot figure out how to resend the requests that previously failed. I also want to get this to work with the resolvers I am currently using.

token.interceptor.ts

return next.handle( request ).do(( event: HttpEvent<any> ) => {
        if ( event instanceof HttpResponse ) {
            // do stuff with response if you want
        }
    }, ( err: any ) => {
        if ( err instanceof HttpErrorResponse ) {
            if ( err.status === 401 ) {
                console.log( err );
                this.auth.collectFailedRequest( request );
                this.auth.refreshToken().subscribe( resp => {
                    if ( !resp ) {
                        console.log( "Invalid" );
                    } else {
                        this.auth.retryFailedRequests();
                    }
                } );

            }
        }
    } );

authentication.service.ts

cachedRequests: Array<HttpRequest<any>> = [];

public collectFailedRequest ( request ): void {
    this.cachedRequests.push( request );
}

public retryFailedRequests (): void {
    // retry the requests. this method can
    // be called after the token is refreshed
    this.cachedRequests.forEach( request => {
        request = request.clone( {
            setHeaders: {
                Accept: 'application/json',
                'Content-Type': 'application/json',
                Authorization: `Bearer ${ this.getToken() }`
            }
        } );
        //??What to do here
    } );
}

The above retryFailedRequests() file is what I can't figure out. How do I resend the requests and make them available to the route through the resolver after retrying?

This is all the relevant code if that helps: https://gist.github.com/joshharms/00d8159900897dc5bed45757e30405f9

Answer 1

My final solution. Works with parallel requests.

UPDATE: The code updated with Angular 9 / RxJS 6, error handling and fix looping when refreshToken fails

import { HttpRequest, HttpHandler, HttpInterceptor, HTTP_INTERCEPTORS } from "@angular/common/http";
import { Injector } from "@angular/core";
import { Router } from "@angular/router";
import { Subject, Observable, throwError } from "rxjs";
import { catchError, switchMap, tap} from "rxjs/operators";
import { AuthService } from "./auth.service";

export class AuthInterceptor implements HttpInterceptor {

    authService;
    refreshTokenInProgress = false;

    tokenRefreshedSource = new Subject();
    tokenRefreshed$ = this.tokenRefreshedSource.asObservable();

    constructor(private injector: Injector, private router: Router) {}

    addAuthHeader(request) {
        const authHeader = this.authService.getAuthorizationHeader();
        if (authHeader) {
            return request.clone({
                setHeaders: {
                    "Authorization": authHeader
                }
            });
        }
        return request;
    }

    refreshToken(): Observable<any> {
        if (this.refreshTokenInProgress) {
            return new Observable(observer => {
                this.tokenRefreshed$.subscribe(() => {
                    observer.next();
                    observer.complete();
                });
            });
        } else {
            this.refreshTokenInProgress = true;

            return this.authService.refreshToken().pipe(
                tap(() => {
                    this.refreshTokenInProgress = false;
                    this.tokenRefreshedSource.next();
                }),
                catchError(() => {
                    this.refreshTokenInProgress = false;
                    this.logout();
                }));
        }
    }

    logout() {
        this.authService.logout();
        this.router.navigate(["login"]);
    }

    handleResponseError(error, request?, next?) {
        // Business error
        if (error.status === 400) {
            // Show message
        }

        // Invalid token error
        else if (error.status === 401) {
            return this.refreshToken().pipe(
                switchMap(() => {
                    request = this.addAuthHeader(request);
                    return next.handle(request);
                }),
                catchError(e => {
                    if (e.status !== 401) {
                        return this.handleResponseError(e);
                    } else {
                        this.logout();
                    }
                }));
        }

        // Access denied error
        else if (error.status === 403) {
            // Show message
            // Logout
            this.logout();
        }

        // Server error
        else if (error.status === 500) {
            // Show message
        }

        // Maintenance error
        else if (error.status === 503) {
            // Show message
            // Redirect to the maintenance page
        }

        return throwError(error);
    }

    intercept(request: HttpRequest<any>, next: HttpHandler): Observable<any> {
        this.authService = this.injector.get(AuthService);

        // Handle request
        request = this.addAuthHeader(request);

        // Handle response
        return next.handle(request).pipe(catchError(error => {
            return this.handleResponseError(error, request, next);
        }));
    }
}

export const AuthInterceptorProvider = {
    provide: HTTP_INTERCEPTORS,
    useClass: AuthInterceptor,
    multi: true
};