Register Charge and Refund Transactions from Your Backend

This feature allows you to register charge and refund transactions in your backend instead of in the app. Use this option if you'd like your backend to initiate the transaction, e.g., because of architectural reasons. You'll receive a
sessionIdentifier
 that you can send down to your app, and then execute the transaction from the app. Use WebHooks to keep your backend informed about the status of the transaction.
Register a Charge Transaction from Your Backend
Before there's anything to pay, your app will most likely be offering some sort of checkout functionality. Information about the purchased items will be transmitted to your backend and your backend will then be able to determine the final amount to be charged.
You will use this information to register a new transaction via an API call to the platform:
POST
/v2/merchants/{merchantIdentifier}/transactionSessions
Request
{
        "transaction" : {
                "amount": 123.34,
                "currency": "EUR",
                "type": "CHARGE",
                "subject": "My subject",
                "customIdentifier": "My custom identifier"
        }
      }
Important Parameters
$.transaction.amount
The amount of money that is about to be charged.
$.transaction.currency
The currency used for the transaction.
$.transaction.type
Use CHARGE to receive money from the shopper.
$.transaction.customIdentifier
An identifier that you can assign to the transaction.
The response body will look something like this:
Response
{
        "status": "ok",
        "data": {
                "validUntil": "2013-09-03 11:18:34",
                "identifier": "0f487dc3-35cd-4125-8b82-631c7d5b328c",
                "transaction": {
                        "identifier": "3fe8fe7c-b620-4b45-b128-545b8c16f236",
                        "customIdentifier": "1234",
                        "status": "INITIALIZED",
                        "subject":  "My subject",
                        "groupIdentifier": "59b57c79-7a04-4e68-9bc1-78dbf71adf32",
                        "processingDetails": {…},
                        "receiptDetails": {…},
                        "type": "CHARGE",
                        "paymentDetails": {…},
                        "locationDetails": {…},
                        "currency": "EUR",
                        "mode": "TEST",
                        "amount": 123.34,
                        "created": "2013-09-03 11:03:34",
                        "statusDetails": {…},
                        "reader": {…}
                }
        }
}
In addition to other information about the transaction, the response body contains two important identifiers:
$.data.identifier
This is the
sessionIdentifier
 that should be returned by you to the app. The app will then use this identifier to start processing the transaction from the mobile device.
$.data.transaction.identifier
The
transactionIdentifier
 should be kept by your backend as a reference to the just registered transaction. It can then be used to do different things such as querying the platform to fetch the current status of a transaction or to cancel the transaction if necessary.
Complete the Transaction in the App with the PayButton
On iOS, provide the
sessionIdentifier
 to
createTransactionViewControllerWithSessionIdentifier
:
[ui createTransactionViewControllerWithSessionIdentifier:@"sessionIdentifier"
                                               completed:^(UIViewController *controller,
                                                           MPUTransactionResult result,
                                                           MPTransaction *transaction)
{
    if (result == MPUTransactionResultApproved) {
        // Payment was approved!
    } else {
        // Payment was declined/aborted!
    }
}];
On Android, provide the
sessionIdentifier
 to
createTransactionIntent
:

Intent intent = ui.createTransactionIntent(sessionIdentifier);
Complete the transaction in the application if you are using the SDK Integration Once you have a
sessionIdentifier
, you can execute the transaction from the app. For iOS, use:

[transactionProvider startPaymentWithSessionIdentifier: /* put your sessionIdentifier here! */  ...];
For Android, use: 

transactionProvider.startPayment(/* put your sessionIdentifier here! */, ...);
How to handle the callbacks of these methods is described here.
Register a Refund Transaction
You only need to use this if you do card present refunds. A different API call is used to implement card not present refunds.
To refund a previously charge transaction, register a refund transaction and pass the
transactionIdentifier
 of the charge transaction as the
referencedTransactionIdentifier
. Provide the exact same
amount
 and
currency
.
post
/v2/merchants/{merchantIdentifier}/transactionSessions
 Try it out!
Request
{
        "transaction" : {
                "referencedTransactionIdentifier": "3fe8fe7c-b620-4b45-b128-545b8c16f236",
                "amount": 123.34,
                "currency": "EUR",
                "type": "REFUND",
                "mode": "TEST",
                "subject": "My Refund"
        }
           }
Important Parameters
$.transaction.referencedTransactionIdentifier
The
transactionIdentifier
 of the previous charge transaction.
$.transaction.amount
The amount of money that is about to be refunded.
$.transaction.currency
The currency used for the transaction.
$.transaction.type
Use REFUND to send money to the shopper.
$.transaction.mode
Use TEST on the test platform, use LIVE on the live platform.