NestJSInterceptors wrap việc thực thi handler, cho phép chạy code trước và sau handler. Chúng implement NestInterceptor với method intercept(context, next) trả về Observable. Gọi next.handle() để tiếp tục pipeline, dùng RxJS operators để transform.
Use-cases phổ biến: Response transform — dùng map() để wrap tất cả response trong object chuẩn { success: true, data, timestamp }. Logging — ghi thời gian xử lý với tap(). Caching — kiểm tra cache trước, nếu hit thì return of(cachedData) bỏ qua handler. Timeout — dùng timeout(5000) throw TimeoutError sau 5 giây. Error mapping — catchError() để transform exceptions.
Apply với @UseInterceptors() ở route/controller hoặc global qua APP_INTERCEPTOR. Khác Guard và Pipe, Interceptors chạy cả trước lẫn sau handler nên có thể transform response.
Interceptors wrap handler execution, allowing code to run both before and after the handler. They implement NestInterceptor with an intercept(context, next) method returning an Observable. Call next.handle() to continue the pipeline, and use RxJS operators to transform.
Common use cases: Response transform — use map() to wrap all responses in a standard { success: true, data, timestamp } object. Logging — record processing time with tap(). Caching — check cache first, if hit return of(cachedData) bypassing the handler. Timeout — use timeout(5000) to throw TimeoutError after 5 seconds. Error mapping — catchError() to transform exceptions.
Apply with @UseInterceptors() at route/controller level or globally via APP_INTERCEPTOR. Unlike Guards and Pipes, Interceptors run both before and after the handler, making them capable of transforming responses.