Custom Middleware — Series 2

Preview — 3 of 10 questions

What does the class form offer that the functional form does not?

javascript

// (1)
export function logger(req: Request, res: Response, next: NextFunction) { next(); }

// (2)
@Injectable()
export class LoggerMiddleware implements NestMiddleware {
  constructor(private readonly config: ConfigService) {}
  use(req: Request, res: Response, next: NextFunction) { next(); }
}

AThe ability to terminate the request without calling next()

BAccess to the route's handler metadata through Reflector

CAutomatic error handling for thrown exceptions

DDependency injection — a class registered in configure() is instantiated by the container, so it can inject services; a plain function is called as-is with no container involvement

Why is the raw body needed here rather than the parsed one?

javascript

const app = await NestFactory.create(AppModule, { rawBody: true });

@Post('webhook')
handle(@Req() req: RawBodyRequest<Request>, @Headers('stripe-signature') sig: string) {
  const event = this.stripe.webhooks.constructEvent(req.rawBody!, sig, secret);
}

ABecause JSON parsing is too slow for high-volume webhook traffic

BBecause the signature is an HMAC over the exact bytes that were sent; re-serialising the parsed object can change key order, spacing or number formatting, producing a different digest and a failed verification

CBecause webhook payloads are not valid JSON

DBecause @Body() is unavailable on POST routes that declare @Headers()

What does passing a controller class to forRoutes() mean?

javascript

configure(consumer: MiddlewareConsumer) {
  consumer.apply(TenantMiddleware).forRoutes(CatsController);
}

AThe middleware applies to every route declared by that controller, including any added later — which keeps the configuration correct as the controller grows

BThe middleware is injected into the controller as a provider

COnly the controller's first route is covered

DThe controller is excluded from the middleware, which is the inverse of exclude()

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