Filters, Interceptors, and AOP: Choosing the Right Spring Tool for Cross-Cutting Concerns

Spring provides three tools — Servlet Filters, Handler Interceptors, and AOP Aspects — to handle cross-cutting concerns like logging, authentication, and metrics without duplicating code across controllers. Filters sit at the outermost layer, operating on raw HTTP requests before Spring even initializes, making them ideal for security gates, CORS headers, and compression. Handler Interceptors run inside Spring's DispatcherServlet and have awareness of which controller method will handle the request, offering hooks before and after the controller executes. AOP Aspects sit deepest in the stack, wrapping individual bean methods and firing even for non-web calls, making them suited for service-layer concerns. The key distinction is depth: as you move inward from Filter to Interceptor to Aspect, each layer gains more Spring context but loses direct access to raw HTTP details.