You can include additional headers and an [idempotency key](https://docs.adyen.com/development-resources/api-idempotency/) in your API requests using the `RequestOptions` object.

~~~~ java

import com.adyen.Client;

import com.adyen.Config;

import com.adyen.enums.Environment;

import com.adyen.model.RequestOptions;

import com.adyen.service.checkout.PaymentsApi;

import com.adyen.model.checkout.PaymentRequest;

import com.adyen.model.checkout.PaymentResponse;

import com.adyen.model.checkout.Amount;

import com.adyen.model.checkout.CardDetails;

import com.adyen.model.checkout.CheckoutPaymentMethod;

import java.util.HashMap;

import java.util.Map;

Config config = new Config()

.environment(Environment.TEST) // Or Environment.LIVE

.apiKey("YOUR_API_KEY");

Client client = new Client(config);

HashMap<String, String> additionalHeaders = new HashMap<>();

additionalHeaders.put("X-Custom-Header", "custom-value");

RequestOptions requestOptions = new RequestOptions()

.idempotencyKey("YOUR_IDEMPOTENCY_KEY") // use UUID

.additionalServiceHeaders(additionalHeaders);

PaymentsApi paymentsApi = new PaymentsApi(client);

CardDetails cardDetails =

new CardDetails()

.type(CardDetails.TypeEnum.SCHEME)

.encryptedCardNumber("5136333333333335")

.holderName("John Doe")

.cvc("737")

.encryptedExpiryMonth("08")

.encryptedExpiryYear("2018");

PaymentRequest paymentRequest =

new PaymentRequest()

.merchantAccount("YOUR_MERCHANT_ACCOUNT")

.reference("YOUR_REFERENCE")

.amount(new Amount()

.currency("EUR")

.value(1000L))

.returnUrl("https://your-company.example.org/checkout?shopperOrder=12xy..")

.paymentMethod(new CheckoutPaymentMethod(cardDetails));

PaymentResponse paymentResponse = paymentsApi.payments(paymentRequest, requestOptions);

System.out.println("Payment response: " + paymentResponse.toJson());

In some setups you might need to deserialize JSON strings to request objects. For example, when using the libraries in combination with [Dropin/Components](https://github.com/Adyen/adyen-web). Please use the built-in deserialization functions:

~~~~ java

assertNotNull(userAgent);

assertEquals(Client.LIB_NAME + "/" + Client.LIB_VERSION, userAgent.getValue());

}

@Test

public void testRequestWithHttpHeaders() throws Exception {

AdyenHttpClient client = new AdyenHttpClient();

HashMap<String, String> additionalHeaders = new HashMap<>();

additionalHeaders.put("X-Custom-Header", "custom-value");

RequestOptions requestOptions =

new RequestOptions()

.idempotencyKey("test-idempotency-key")

.additionalServiceHeaders(additionalHeaders);

HttpUriRequestBase request =

client.createRequest(

"https://checkout-test.adyen.com/v68/payments",

"{}",

new Config(),

true,

requestOptions,

ApiConstants.HttpMethod.POST,

Map.of());

Header idempotencyKeyHeader = request.getFirstHeader("Idempotency-Key");

assertNotNull(idempotencyKeyHeader);

assertEquals("test-idempotency-key", idempotencyKeyHeader.getValue());

Header customHeader = request.getFirstHeader("X-Custom-Header");

assertNotNull(customHeader);

assertEquals("custom-value", customHeader.getValue());

}

}