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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11In a standard Spring Boot servlet application, Tomcat accepts the HTTP request, registered servlet filters run, and Spring MVC’s DispatcherServlet delegates it to a matching controller method. The method’s return value then becomes part of the HTTP response, often through a message converter. Tomcat handles the servlet-container layer; Spring MVC handles the controller dispatch.
The two layers: embedded Tomcat and Spring MVC
Spring Boot configures and starts an embedded servlet server for a servlet-based application. Tomcat is one supported choice; Jetty and Undertow are alternatives. In the Spring Boot 3.3 reference, the default embedded server port is 8080. The application context obtains a ServletWebServerFactory, whose implementation creates the selected server. Spring Boot 3.3: Servlet Web Applications
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Tomcat is not the component that understands @RestController. It provides the servlet container that receives and dispatches servlet requests. Spring MVC supplies the DispatcherServlet and the machinery that matches requests to application handlers.
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How a request reaches a controller
For the ordinary Spring MVC path, the sequence is:
HTTP client → embedded Tomcat connector → servlet filters → DispatcherServlet → handler mapping and adapter → @RestController method → HttpMessageConverter → HTTP response
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This is a conceptual request flow, not a description of Tomcat’s internal socket, protocol, or thread implementation. Each stage has a distinct responsibility.
1. Tomcat receives the request and filters run
The servlet container receives the HTTP request and applies registered servlet filters before dispatching to the servlet mapped for the URL. Spring Boot can register servlet and filter beans with the embedded container. In the standard arrangement, a single servlet maps to / and filters map to /*; additional registrations, URL patterns, or ordering choices can change which requests pass through which filters. Spring Boot 3.3: Servlet registration
Filters operate at the servlet-container boundary. They can affect a request before it reaches Spring MVC, but they do not select a Spring controller method.
2. DispatcherServlet takes the front-controller role
In Spring MVC, the servlet handling the application’s MVC requests is normally DispatcherServlet. The Spring Framework describes the front-controller pattern this way: “Spring MVC, as many other web frameworks, is designed around the front controller pattern where a central Servlet, the DispatcherServlet, provides a shared algorithm for request processing, while actual work is performed by configurable delegate components.” Spring Framework Reference: DispatcherServlet
In other words, the dispatcher coordinates request processing; it is not the container and does not contain every routing rule itself.
3. Spring MVC matches the request to a handler
Spring MVC’s handler-mapping components compare request details with registered mappings. In annotation-driven controllers, those mappings are declared with @RequestMapping and composed annotations such as @GetMapping. If a mapping matches, an MVC handler adapter invokes the selected method and Spring MVC resolves its parameters. Tomcat does not inspect these annotations or choose the method. Spring Boot 3.3: Spring MVC
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Path matching is configurable and version-sensitive. Spring Boot 3.3 documents PathPatternParser as the default strategy and describes its customization and restrictions; do not assume every pattern behaves identically across Boot releases or configurations. Spring Boot 3.3: Spring MVC
4. The controller method returns response data
@RestController is a Spring MVC annotation, not a Spring Boot-only feature. It combines @Controller with @ResponseBody, so the method’s return value is handled as response content rather than as a view name. A plain @Controller commonly returns a view name, although its methods can also use response-body behavior when configured to do so. Spring Getting Started: Building a RESTful Web Service Spring Boot Reference: Spring MVC annotations
5. A message converter writes the HTTP representation
Spring MVC selects a suitable HttpMessageConverter to turn the returned value into response content. The available converters and the negotiated media type affect what the client receives; the request’s Accept header can be part of that negotiation. A returned object does not guarantee JSON in every application, because dependencies, response type, configuration, and available representations matter.
For Spring Boot 4.1.1 specifically, the how-to guide describes default JSON rendering when Jackson 3 is available. That release-specific detail should not be treated as a requirement for earlier Boot versions. Spring Boot 4.1.1: Spring MVC
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What can change the usual path?
- Filters and servlet mappings: Applications can register additional filters or servlets, change URL mappings, or customize filter order.
- Other request destinations: A request may be handled by another servlet, a static-resource handler, or an error path rather than a controller method.
- Custom MVC configuration: Handler mappings and path-matching configuration can alter which controller, if any, matches.
- Application stack: This flow describes Spring MVC on the servlet stack. It should not be conflated with Spring WebFlux request handling.
- Boot release: Defaults and implementation details can vary by version, so verify claims against the documentation for the application’s release.
Boot’s auto-configuration makes the conventional MVC setup convenient when the relevant dependencies are present, but neither the routing annotations nor @RestController are proprietary Boot annotations. Spring Getting Started: Building a RESTful Web Service Spring Boot Reference: Spring MVC annotations
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