Angular 4 : unable to read headers from response - not a CORS issue

Question

在服务器自动更新 token 的情况下，我在基础知识上苦苦挣扎:从响应中获取 header 数据。

它似乎与 CORS 无关，因为我的 Node/express allwos Authorization/x-access-token 并相应地做出响应(参见下面的网络选项卡屏幕截图)。

我希望看到工作的第一步只是从响应中读取 header 。查看我的代码，它是在文档中找到的样板。获取“Content-Length”的事件返回 null。

auth-service.ts

login(username:string, password:string):Observable<boolean>{
    this.loggedIn = false;
    return new Observable( (observer:Observer<boolean>) => {

      const body = {user: username, pwd: password};
      const url = this.config.API_ENDPOINT_PUBLIC_AUTH;

      this.httpClient.post(url, body, {
        responseType: 'text',
        observe: "response"
      }).first().subscribe(
        (response:HttpResponse<string>) => {

          // DEBUG
          console.log(response.headers.get('Authorization'));
          console.log(response.headers.get('X-Test-Header'));
          console.log(response.headers.get('Content-length'));


          this.token = response.headers.get('Authorization');
          this.storeToken(this.token);
          this.currentUser = username;
          this.loggedIn = true;
          this.authChanged$.next('auth');
          observer.next(true);
        },
        (err) => observer.next(false),
        () => {},
      );
    });
  }

控制台输出:

null

null

null

将此与此请求的我的网络选项卡的内容进行比较:

不用说我的 HttpInterceptor 也不起作用 - 在响应中提供“授权” header 后，它使用该值作为新 token 。这是为了实现 token 的自动更新:

token.interceptor.ts

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

    const authService = this.injector.get(AuthService);
    const token = authService.getToken();

    if(token){
      request = request.clone({
        setHeaders: { 'x-access-token' : token }
      });
    }
    
    return next.handle(request).do(
      (event: HttpEvent<any>) => {
        if (event instanceof HttpResponse) {
          const response:HttpResponse<any> = (<HttpResponse<any>> event);
          const authorizationHeader = response.headers.get('Authorization');
          console.log('Authorization header value: ' + authorizationHeader);
          if(authorizationHeader){
            authService.setToken(authorizationHeader);
          }
        }
      },
      (err: any) => {
      if (err instanceof HttpErrorResponse){
        if (err.status === 401) {
          this.router.navigate(['/']);
        }
      }
    });
  }

Answer 1

好的，这就是答案:我使用 Node.js/Express 作为后端，即使 header 在 Chrome 的网络选项卡中可见，它也无法让 Angular 处理它们。

“怎么看得见却不能用？”我还是不清楚。

配置您的 Node/Express 应用(查找评论“SOLUTION HERE”):

function configureExpress(expressApp){  
    expressApp.use(bodyparser.urlencoded({ extended: true }));
    expressApp.use(bodyparser.json());

    // Middleware: Use CORS, add headers and allow methods
    expressApp.use(expressMiddleware);
}

function expressMiddleware(req, res, next) {

    // Request origin: Allow ALL
    res.header("Access-Control-Allow-Origin", "*");

    // Allowed headers
    res.header("Access-Control-Allow-Headers",

        "Origin"
        +",X-Requested-With"   // Dont allow AJAX CORS without server consent - see http://stackoverflow.com/questions/17478731/whats-the-point-of-the-x-requested-with-header
        +",x-access-token"
        +",Content-Type"
        +",Authorization"
        +",Accept"
    );

    // SOLUTION HERE
    // Allow headers access
    res.header("access-control-expose-headers",
        ",Authorization"
        +",Content-Length"
        );

    // Allowed methods
    res.header('Access-Control-Allow-Methods',
        'GET,'
        +',POST'
        +',OPTIONS'
        +',PUT,'
        +',DELETE'
    );

    // Handle CORS requests: cross-domain/origin requests will begin with an OPTION request to the same endpoint.
    if('OPTIONS' === req.method){
        res.sendStatus(200);
    }

    else{
        // Request validations complete
        next();
    }
}