transfer/get json to javascript rest api from rest controller

to me need integrate javascript rest api with app on spring-boot, rest api gets json and making URL. How to call a method in a rest controller in javascript and get json? Help me please

Controller:

@RestController
@RequestMapping("/api/v1/vk-pay")
public class VKPayController {

    private final PaymentService paymentService;

    @Autowired
    public VKPayController(@Qualifier("VKPayServiceImpl") PaymentService paymentService) {
        this.paymentService = paymentService;
    }

    @GetMapping("/{id}")
    private Parameters getParams(@PathVariable("id") Long orderId,
                             @AuthenticationPrincipal UserDetails user){
        VKPayPayment payment = paymentService.createOrder("captureUrl", orderId);
        paymentService.save(payment,user.getUsername(),orderId);
        return payment.getParam();
    }
}

javascript:

params = how to get json from restcontroller?
VK.App.open('vkpay', '''params''');