WayForPay.java

public class WayForPayClient {
    private final RestTemplate restTemplate;
    private final WayForPayProperties wayForPayProperties;

    public void createPayment(SubscriptionType subscriptionType, Long userId) {
        String formUrl = "https://secure.wayforpay.com/pay";

        String orderReference = subscriptionType.name() + ":"+userId + ":" + System.currentTimeMillis();
        long time = System.currentTimeMillis();

        MultiValueMap<String, String> formData = new LinkedMultiValueMap<>();
        formData.add("merchantAccount", wayForPayProperties.getMerchantAccount());
        formData.add("merchantAuthType", "SimpleSignature");
        formData.add("merchantDomainName", "www.market.ua");
        formData.add("orderReference", orderReference);
        formData.add("orderDate", String.valueOf(time));
        formData.add("amount", "1547.36");
        formData.add("currency", "UAH");
        formData.add("orderTimeout", "49000");
        formData.add("productName[]", "Процессор Intel Core i5-4670 3.4GHz");
        formData.add("productName[]", "Память Kingston DDR3-1600 4096MB PC3-12800");
        formData.add("productPrice[]", "1000");
        formData.add("productPrice[]", "547.36");
        formData.add("productCount[]", "1");
        formData.add("productCount[]", "1");
        formData.add("clientFirstName", "Вася");
        formData.add("clientLastName", "Пупкин");
        formData.add("clientAddress", "пр. Гагарина, 12");
        formData.add("clientCity", "Днепропетровск");
        formData.add("clientEmail", "some@mail.com");
        formData.add("defaultPaymentSystem", "card");

        String signature = WayForPayUtils.createPaymentSignature(formData, wayForPayProperties.getMerchantSecretKey());
        formData.add("merchantSignature", signature);

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

        HttpEntity<MultiValueMap<String, String>> requestEntity = new HttpEntity<>(formData, headers);

        ResponseEntity<String> response = restTemplate.exchange(formUrl, HttpMethod.POST, requestEntity, String.class);

        String responseBody = response.getBody();
    }
}