Angular 7：拦截器中的等待函数

Question

我在我的第一个 Angular 应用程序中构建了一个错误拦截器，这对我来说是全新的。当出现401 响应代码时，拦截器会尝试刷新 Firebase 授权令牌。因此，我编写了以下代码：

@Injectable()
export class ErrorInterceptor implements HttpInterceptor {
constructor(private authService: AuthService, private alertService: AlertService) { }

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request).pipe(
        catchError(err => {
            if (err.status === 401) {
                let user = localStorage.getItem('currentUser');
                if (!user) {
                    this.logout(false);
                    return throwError(err.error);
                }
                let currentUser = JSON.parse(user);
                if (!currentUser || !currentUser.stsTokenManager || !currentUser.stsTokenManager.accessToken) {
                    this.logout(false);
                    return throwError(err.error);
                }
                const reference = this;
                this.authService.getToken(currentUser, true).then(t => {
                    // How do I await and return this properly?
                    return reference.updateTokenAndRetry(request, next, currentUser, t);
                }); // Get token and refresh
            }
            this.alertService.showAlert({
                text: 'Fout tijdens het verzenden van het verzoek',
            });
            return throwError(err.error);
        })
    );
}

updateTokenAndRetry(request: HttpRequest<any>, next: HttpHandler, currentUser: any, token: string): Observable<HttpEvent<any>> {
    // Update local stored user
    currentUser.stsTokenManager.accessToken = token;
    localStorage.setItem('currentUser', JSON.stringify(currentUser));

    // Add the new token to the request
    request = request.clone({
        setHeaders: {
            Authorization: token,
        },
    });

    return next.handle(request);
}

令牌可以正常刷新。但是刷新后网络调用没有被执行，reference.updateTokenAndRetry(request, next, currentUser, t); 应该这样做。

我认为这是因为this.authService.getToken(currentUser, true) 返回了Promise（这是 Firebase 插件，无法更改）。我想返回return reference.updateTokenAndRetry(request, next, currentUser, t);，但这是不可能的，因为它位于异步功能块中。

如何等待或返回下一个网络调用？我无法创建intercept 函数async。在这一点上我很困惑。

Answer 1

您应该使用 RxJS 'from' 运算符将您的 Promise 转换为 observable，而不是尝试返回异步 Promise，如本文所述：Convert promise to observable。

这将为您的拦截器生成正确的 Observable 返回类型。

您的代码如下所示（假设您一次只发送一个请求）：

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    return next.handle(request).pipe(
        catchError(err => {
            if (err.status === 401) {
                let user = localStorage.getItem('currentUser');
                if (!user) {
                    this.logout(false);
                    return throwError(err.error);
                }
                let currentUser = JSON.parse(user);
                if (!currentUser || !currentUser.stsTokenManager || !currentUser.stsTokenManager.accessToken) {
                    this.logout(false);
                    return throwError(err.error);
                }
                // Return a newly created function here
                return this.refreshToken(currentUser, request, next);
            }
            this.alertService.showAlert({
                text: 'Fout tijdens het verzenden van het verzoek',
            });
            return throwError(err.error);
        })
    );
}

refreshToken(currentUser: any, request: any, next: any) {
    // By making use of the from operator of RxJS convert the promise to an observable
    return from(this.authService.getToken(currentUser, true)).pipe(
        switchMap(t => this.updateTokenAndRetry(request, next, currentUser, t))
    )
}

updateTokenAndRetry(request: HttpRequest<any>, next: HttpHandler, currentUser: any, token: string): Observable<HttpEvent<any>> {
    // Update local stored user
    currentUser.stsTokenManager.accessToken = token;
    localStorage.setItem('currentUser', JSON.stringify(currentUser));

    // Add the new token to the request
    request = request.clone({
        setHeaders: {
            Authorization: token,
        },
    });

    return next.handle(request);
}

希望这会有所帮助！

Answer 2

Arwin 解决方案运行良好，但仅适用于同时发送一个请求的环境。

为了让它工作，将 refreshToken 方法保存到带有管道 share 的 Observable 中。这将允许多个订阅者但只有一个结果。

将next.handle(request) 方法包装在另一个Subject<any> 中并返回主题。 如果请求触发不是401 错误调用subject.error 的错误调用。

在刷新令牌后调用this.updateTokenAndRetry(request, next, currentUser, token).subscribe(result => subject.next(result); 以确保将请求返回给初始订阅者。

以下代码是伪代码，应该适用于您的情况。

refreshTokenObservable: Observable<any>;

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {

    let subject = new Subject<any>();

    next.handle(request).pipe(
        catchError(err => {
            if (err.status === 401) {
                let user = localStorage.getItem('currentUser');
                if (!user) {
                    this.logout(false);
                    subject.error(err.error);
                    return;
                }
                let currentUser = JSON.parse(user);
                if (!currentUser || !currentUser.stsTokenManager || !currentUser.stsTokenManager.accessToken) {
                    this.logout(false);
                    subject.error(err.error);
                    return;
                }
                // Return a newly created function here
                this.refreshToken(currentUser).subscribe(token => {

                    this.updateTokenAndRetry(request, next, currentUser, token).subscribe(result => subject.next(result);
                    this.refreshTokenObservable = null; // clear observable for next failed login attempt
                });
            }
            this.alertService.showAlert({
                text: 'Fout tijdens het verzenden van het verzoek',
            });
            subject.error(err.error);
        })
    ).subscribe(result => subject.next(result));

    return subject.asObservable();
}

refreshToken(currentUser: any) {

    if(this.refreshTokenObservable == null)
    {
        // By making use of the from operator of RxJS convert the promise to an observable
        this.refreshTokenObservable = from(this.authService.getToken(currentUser, true)).pipe(share());
    }

    return this.refreshTokenObservable;
}

updateTokenAndRetry(request: HttpRequest<any>, next: HttpHandler, currentUser: any, token: string): Observable<HttpEvent<any>> {
    // Update local stored user
    currentUser.stsTokenManager.accessToken = token;
    localStorage.setItem('currentUser', JSON.stringify(currentUser));

    // Add the new token to the request
    request = request.clone({
        setHeaders: {
            Authorization: token,
        },
    });

    return next.handle(request);
}