@RequestParam vs @PathVariable vs @RequestBody.

1. @PathVariable:

Used to extract values from the URL template.

• URL: /users/123
• Code: @GetMapping("/users/{id}") public User get(@PathVariable String id) { ... }

2. @RequestParam:

Used for query parameters (key-value pairs) in the URL.

• URL: /users?id=123
• Code: @GetMapping("/users") public User get(@RequestParam String id) { ... }

3. @RequestBody:

Used to extract the body of the request (typically JSON) and deserialize it into a Java object.

• Code: @PostMapping("/users") public void save(@RequestBody User user) { ... }