Applies to: In-App Payments SDK - Android | In-App Payments SDK - iOS
Learn how to connect a mobile application to a backend service.
Connect to a Backend Service
- Follow the steps in Build on Android.
- If you don't have a payment processing backend available for testing, follow Deploy the Server to start a small backend service suitable for testing.
To validate and process the payment token returned by the SDK CardEntry object, you must send it to a backend service that uses Connect payment APIs to capture payment.
To set up the backend connection, build a Retrofit object and configure it with the base URL for your backend service.
public class ConfigHelper {
private static final String CHARGE_SERVER_HOST = "REPLACE_ME";
private static final String CHARGE_SERVER_URL = "https://" + CHARGE_SERVER_HOST + "/";
public static boolean serverHostSet() {
return !CHARGE_SERVER_HOST.equals("REPLACE_ME");
}
public static Retrofit createRetrofitInstance() {
return new Retrofit
.Builder()
.baseUrl(ConfigHelper.CHARGE_SERVER_URL)
.addConverterFactory(MoshiConverterFactory.create())
.build();
}
}public interface ChargeService {
@POST("/chargePaymentCard")
Call<Void> charge(@Body ChargeRequest request);
class ChargeErrorResponse {
String errorMessage;
}
class ChargeRequest {
final String nonce;
ChargeRequest(String nonce) {
this.nonce = nonce;
}
}
}To use your REST interface, create a Call<ChargeResult> implementation that packages and sends requests to the payment processing backend.
public class ChargeCall implements Call<ChargeResult> {
public static class Factory {
private final ChargeService service;
private final Converter<ResponseBody, ChargeService.ChargeErrorResponse> errorConverter;
public Factory(Retrofit retrofit) {
service = retrofit.create(ChargeService.class);
Annotation[] noAnnotations = {};
Type errorResponseType = ChargeService.ChargeErrorResponse.class;
errorConverter = retrofit.responseBodyConverter(errorResponseType, noAnnotations);
}
public Call<ChargeResult> create(String nonce) {
return new ChargeCall(this, nonce);
}
}
private final ChargeCall.Factory factory;
private final String nonce;
private final retrofit2.Call<Void> call;
private ChargeCall(ChargeCall.Factory factory,
String nonce) {
this.factory = factory;
this.nonce = nonce;
call = factory.service.charge(new ChargeService.ChargeRequest(nonce));
}
@Override
public ChargeResult execute() {
Response<Void> response;
try {
response = call.execute();
} catch (IOException e) {
return ChargeResult.networkError();
}
return responseToResult(response);
}
@Override
public void enqueue(sqip.Callback<ChargeResult> callback) {
call.enqueue(new Callback<Void>() {
@Override
public void onResponse(@NonNull retrofit2.Call<Void> call, @NonNull Response<Void> response) {
callback.onResult(responseToResult(response));
}
@Override
public void onFailure(@NonNull retrofit2.Call<Void> call, Throwable throwable) {
if (throwable instanceof IOException) {
callback.onResult(ChargeResult.networkError());
} else {
throw new RuntimeException("Unexpected exception", throwable);
}
}
});
}
//TODO: Define the ChargeResult method in step 4.
… //additional required Call<ChargeResult> methods
}Define a ChargeResult object and act on the results.
private ChargeResult responseToResult(Response<Void> response) {
if (response.isSuccessful()) {
return ChargeResult.success();
}
try {
//noinspection ConstantConditions
ResponseBody errorBody = response.errorBody();
ChargeService.ChargeErrorResponse errorResponse = factory.errorConverter.convert(errorBody);
return ChargeResult.error(errorResponse.errorMessage);
} catch (IOException exception) {
return ChargeResult.networkError();
}
}