Springmedium

`@RequestParam` vs `@PathVariable` — when do you use which?

Answer

Use `@PathVariable` for identifiers that are part of the resource path (e.g., `/users/{id}`). Use `@RequestParam` for optional filters, pagination, or query options (e.g., `?page=2&sort=name`).

@GetMapping("/users/{id}")
UserDto getUser(@PathVariable String id, @RequestParam(defaultValue = "false") boolean verbose) {
  return service.get(id, verbose);
}

Advanced answer

Deep dive

Expanding on the short answer — what usually matters in practice:

Context (tags): spring-mvc, requestparam, pathvariable, rest
Lifecycle: what happens at runtime (render/build, request/response, background jobs).
Caching: where cache lives, cache keys, how to invalidate without chaos.
Security: authn/authz, secrets, attack surface (SSRF/CSRF).
Explain the "why", not just the "what" (intuition + consequences).
Trade-offs: what you gain/lose (time, memory, complexity, risk).
Edge cases: empty inputs, large inputs, invalid inputs, concurrency.

Examples

Here’s an additional example (building on the short answer):

@GetMapping("/users/{id}")
UserDto getUser(@PathVariable String id, @RequestParam(defaultValue = "false") boolean verbose) {
  return service.get(id, verbose);
}

Common pitfalls

Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).
Ignoring constraints: memory, concurrency, network/disk costs.

Interview follow-ups

When would you choose an alternative and why?
What production issues show up and how do you diagnose them?
How would you test edge cases?