How to avoid multiple HttpInterceptor calls while navigating between RxJS mergeMap?

问题

I'm using two JWT tokens - Refresh Token(expires after 7 days) and Access Token (expires after 15 min). They are stored on httpOnly cookies and can be accessed via server. Refresh methods signs new token and store it on a cookie. I need to check if these tokens are expired after every request like this:

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

    constructor(private authService: AuthService, private cookieService: CookieService) { }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
            const expirationToken = this.cookieService.get('tokenexp'); // access token expiration
            const expirationTokenRefresh = this.cookieService.get('tokenrefexp'); // refresh expiration
            
            // refresh token -> access token -> original request
            return of(Number(expirationTokenRefresh) < Date.now()).pipe(
              mergeMap(expire => expire
                ? this.authService.refreshTokenRefresh()
                : of(Number(expirationToken) < Date.now())
              ),
              mergeMap(expire => expire
                ? this.authService.refreshToken()
                : of(true)
              ),
              mergeMap(ok => next.handle(req.clone({ withCredentials: true })))
            );
    }

}

// auth service
refreshToken() {
  return this.http.get(`${BACKEND_URL}/refreshtoken`);
}
refreshTokenRefresh() {
  return this.http.get(`${BACKEND_URL}/refreshtokenref`);
}

I may send one request to refresh a token, and then another request to refresh second token, and finally the original request with updated cookies. In summary, I may need to send requests before my original request.

Problem is: There is a loop of requests going to AuthInterceptor every time a request is made. Request one and two (tokens) shouldn't call AuthInterceptor.

回答1:

Do a conditional check to skip the interceptor if the request url is for token.

@Injectable()
export class AuthInterceptor implements HttpInterceptor {

    constructor(private authService: AuthService, private cookieService: CookieService) { }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    
            if(req.url===`${BACKEND_URL}/refreshtoken` || req.url ===`${BACKEND_URL}/refreshtokenref`)
              return next.handle(req.clone({ withCredentials: true }))
            
            const expirationToken = this.cookieService.get('tokenexp'); // access token expiration
            const expirationTokenRefresh = this.cookieService.get('tokenrefexp'); // refresh expiration
            
            // refresh token -> access token -> original request
            return of(Number(expirationTokenRefresh) < Date.now()).pipe(
              mergeMap(expire => expire
                ? this.authService.refreshTokenRefresh()
                : of(Number(expirationToken) < Date.now())
              ),
              mergeMap(expire => expire
                ? this.authService.refreshToken()
                : of(true)
              ),
              mergeMap(ok => next.handle(req.clone({ withCredentials: true })))
            );
    }

}

// auth service
refreshToken() {
  return this.http.get(`${BACKEND_URL}/refreshtoken`);
}
refreshTokenRefresh() {
  return this.http.get(`${BACKEND_URL}/refreshtokenref`);
}

Do agree to @Xinan that interceptor can sometimes be more of a problem. Create your own http service might be better

class HttpService{
   constructoer(private _http:HttpClient)

   preIntercept(url,options){
     this._http.get(tokenUrl).pipe(
       map(res=>{
           //do your stuff
            return {url,options}
        }))

}

get(url,options={}){
    return this.preIntercept(url,options).pipe(
    mergeMap(({url,options})=>this._http.get(url,options))
}

}

来源：https://stackoverflow.com/questions/52781145/how-to-avoid-multiple-httpinterceptor-calls-while-navigating-between-rxjs-mergem