Building REST Services

Standard MVC Controllers return logical "View" template labels mapping to HTML code. REST APIs explicitly return serialized text formats (like JSON).

`@RestController`

In Spring, a REST API structure is achieved via @RestController. This annotation combines @Controller and @ResponseBody internally, forcing Java object conversion to generic JSON upon HTTP return.

@RestController
@RequestMapping("/api/v1/users")
public class UserRestController {

    private final UserService userService;

    public UserRestController(UserService userService) {
        this.userService = userService;
    }

    @GetMapping("/{id}")
    public ResponseEntity<User> getUserById(@PathVariable Long id) {
        User user = userService.findById(id);
        
        // Returns generic mapped JSON code
        return ResponseEntity.ok(user);
    }
}

@RestController​

`@RestController`