angular-interceptors

Angular HttpClient requests receive auth tokens centrally by implementing functional HttpInterceptorFn to attach Bearer headers. Register ordered interceptors via provideHttpClient with withInterceptors so all outgoing API calls carry authentication without modifying individual services.

Handle 401 errors by catching HttpErrorResponse within interceptors using RxJS stream operators. Centralize error handling to trigger logout or route navigation workflows to /login directly from the HTTP interceptor pipeline without duplicating logic in individual services.

Enable caching for specific HTTP requests using HttpContext and HttpContextToken. Set per-request flags to apply special handling, allowing interceptors to conditionally execute caching logic only when the token is passed with the request.

Angular 21 supports functional interceptors via HttpInterceptorFn, enabling auth token attachment and header transformation without class boilerplate. Register them using provideHttpClient with withInterceptors for predictable processing order across logging and error handling.

Log request and response timings using functional interceptors within the HttpClient pipeline. Intercept HttpEvents using RxJS stream operators to measure and log durations centrally, keeping individual services thin and consistent.

Ensure predictable processing order by registering ordered functional interceptors via provideHttpClient with withInterceptors. Compose logging, auth, and error handling interceptors sequentially so each stage processes the HttpEvent stream exactly as arranged.