DispatcherServlet in Spring MVC — Front Controller Pattern

Direct Answer

DispatcherServlet is Spring MVC's front controller servlet. It handles requests mapped to that servlet, finds a handler through HandlerMapping, invokes it through a HandlerAdapter, and coordinates body writing, view rendering, and exception resolution. It does not intercept literally every HTTP request: servlet mappings, filters, static-resource handling, and other servlets determine which requests reach it.

Code Example

@RestController
@RequestMapping("/api/orders")
public class OrderController {
    
    @GetMapping("/{id}")
    public Order getOrder(@PathVariable Long id) {
        // DispatcherServlet already intercepted this request
        // HandlerMapping found this method matches GET /api/orders/{id}
        // Now control reaches here
        return new Order(id, "Laptop", 1200.0);
        // DispatcherServlet will use Jackson to convert Order to JSON
    }
}

record Order(Long id, String item, Double price) {}

// Spring Boot auto-configuration equivalent (you don't write this):
// @Bean
// public DispatcherServlet dispatcherServlet() {
//     var servlet = new DispatcherServlet();
//     servlet.setContextClass(AnnotationConfigWebApplicationContext.class);
//     return servlet;
// }

Common Mistakes & Pitfalls

• Thinking controllers are servlets: Freshers often believe each @RestController is a servlet that directly receives HTTP requests. In reality, controllers are plain Spring beans — DispatcherServlet is the only servlet, and it delegates to controllers.
• Not understanding why URL patterns matter: If you manually register DispatcherServlet with pattern /api/*, requests to /health won't reach it. Spring Boot registers it at / so all requests go through it.
• Assuming DispatcherServlet does business logic: It's purely a coordinator — it routes requests, invokes handlers, and formats responses, but never contains your domain logic.