@RestController
@RequestMapping("/api")
public class Sorting {

    @PostMapping(value = "/sortUsers/{field}/{type}")
    public List<UserDTO> sortUsers(@RequestBody List<UserDTO> userDTOS, @PathVariable String field, @PathVariable String type) {
        if (field.equals("firstname")) {
            if (type.equals("asc")) {
                userDTOS.sort(Comparator.comparing(UserDTO::getFirstName));
            } else {
                userDTOS.sort(Comparator.comparing(UserDTO::getFirstName).reversed());
            }
        } else if (field.equals("lastname")) {
            if (type.equals("asc")) {
                userDTOS.sort(Comparator.comparing(UserDTO::getFirstName));
            } else {
                userDTOS.sort(Comparator.comparing(UserDTO::getLastName).reversed());
            }
        }
        return userDTOS;
    }
}