Angular interceptor http call

Question

I have an application that gets a JWT from his backend. This JWT is valid for 15 minutes. When I send the JWT from the frontend to the backend, a HTTP interceptor appends the JWT to the Authorization header.

What I try to do is:

In the Http interceptor check if the token is still valid, if not send a request to the backends endpoint to get a new JWT.

My problem is: if I intercept every call to append the header, I will walk into a loop if I do a http request in the interceptor itself.

This is my interceptor:

intercept(req: HttpRequest<any>, next: HttpHandler) {
  let authReq = req;
  const token = this.userService.getUserInfo()?.token;
  const jwtHelper: JwtHelperService = new JwtHelperService();
  if (token != null) {
    if (!jwtHelper.isTokenExpired(token)) {
      authReq = req.clone({headers: req.headers.set(TOKEN_HEADER_KEY, 'Bearer ' + token)});
    } else {
      this.authenticationService.getToken();
    return;
    }
  }
  return next.handle(authReq);
}

What is the right way to do this?

noam steiner noam steiner · Accepted Answer · 2020-07-18T17:42:11

The server should handle the validity of the token, it's not the client's logic.

Send the request with the token, if the response will have a 401/403/whatever status send a request for a new token.

Angular interceptor http call

1 Answers