I Built an Interactive Visualizer of the Spring Boot Request Lifecycle

Every Spring tutorial teaches you the annotations — @RestController, @Service, @Repository — but almost none show you the journey a single HTTP request takes between them. Where does the front controller sit? When does @Valid short-circuit? Where exactly is a 404 born?

So I built an interactive visualizer that animates the whole thing, right in the browser.

▶ Live demo: https://dev48v.github.io/spring-request-flow/

Source (zero dependencies): https://github.com/dev48v/spring-request-flow

Click an endpoint, hit Send, and watch the request flow down through every layer and back up as JSON — with a live trace log and the real response.