Spring MVC Request Lifecycle, Filters, and Async

Place each cross-cutting concern in exactly one hook and name the hook in the code. Spring MVC offers several insertion points; picking the wrong one produces work that runs twice, skips the error path, or misses non-controller requests.

When to use

• A @RestController endpoint returns the wrong status, body, or media type.
• Deciding between a Filter, a HandlerInterceptor, a @ControllerAdvice, and an argument resolver, or debugging a hook that does not run.
• Adding Callable, DeferredResult, SseEmitter, or ResponseBodyEmitter handling, and deciding where virtual threads help.

When not to use

• Status codes, problem shapes, and versioning policy belong to spring-boot-rest-api.
• Request and response record shape belongs to spring-boot-dto.
• Bean Validation constraints on bodies and parameters belong to spring-boot-validation.
• Authentication, authorization, and CORS enforcement belong to spring-boot-security.
• Package placement, controller test slices, and MockMvc mechanics belong to spring-boot-clean-architecture and spring-boot-integration-testing.

Ownership and sibling boundaries