HandlerMapping in Spring MVC — URL to Controller Method Resolution

Direct Answer

HandlerMapping is the Spring MVC strategy that finds a handler for an incoming request. For annotated controllers, RequestMappingHandlerMapping registers @RequestMapping, @GetMapping, and similar methods at startup, then matches requests by their mapping conditions and returns the handler together with applicable interceptors.

Code Example

@RestController
@RequestMapping("/api/products")
public class ProductController {
    
    @GetMapping("/{id}")
    public Product getProduct(@PathVariable Long id) {
        // RequestMappingHandlerMapping mapped GET /api/products/123 to this method
        return new Product(id, "Gaming Mouse", 59.99);
    }
    
    @PostMapping
    public Product createProduct(@RequestBody Product product) {
        // POST /api/products mapped here by HTTP method
        return product;
    }
}

record Product(Long id, String name, Double price) {}

// During startup, RequestMappingHandlerMapping scans this controller:
// Map entry: GET /api/products/{id} -> ProductController.getProduct(Long)
// Map entry: POST /api/products -> ProductController.createProduct(Product)
// 
// At runtime, when DispatcherServlet receives GET /api/products/5:
// HandlerMapping.getHandler(request) returns HandlerExecutionChain pointing to getProduct

Common Mistakes & Pitfalls

• Not knowing HandlerMapping exists: Learners think Spring "just knows" which method to call. They don't realize DispatcherServlet delegates to HandlerMapping for this lookup. When routing breaks, they don't know where to look.
• Assuming only one HandlerMapping: Spring registers several by default — RequestMappingHandlerMapping for controllers, SimpleUrlHandlerMapping for static resources. If you register a custom one without setting order, it might not run.
• Conflicting mappings without realizing: Writing two methods with @GetMapping("/users/{id}") and @GetMapping("/users/{name}") causes AmbiguousMappingException at startup because HandlerMapping can't distinguish them — Learners think "oh, one's an id, one's a name" but HandlerMapping sees identical patterns.