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External payment gateways

How to manage payments and transactions via external services
Commerce Layer is integrated with some of the most popular payment gateways — Adyen, Braintree, Checkout.com, Klarna, Paypal, and Stripe. They are all compliant with the PSD2 European regulation so that you can implement a payment flow that supports SCA and 3DS2.
Adding new payment gateways to our core is already provided for in our roadmap. Anyway, you already have the complete flexibility to connect to whichever payment service provider you may need. To do that, just create an external payment gateway and define your custom endpoint(s) responding to the following actions:
  1. 1.
    Authorization — to authorize a payment source
  2. 2.
    Capture — to capture an authorization
  3. 3.
    Void — to void an authorization
  4. 4.
    Refund — to refund a capture, either totally or partially
  5. 5.
    Customer token — to create a customer payment token
Your external endpoint will be responsible for the actual integration with the payment gateway. The payment source associated with the order must be an external payment.
External gateways process payments synchronously by default. If you need your gateway to behave differently, check the asynchronous payments section.

Request

The request payload is a JSON:API compliant object you can query to perform your own computation. Aside from the target resource — which depends on the kind of gateway's transaction — some relationships are also included to avoid useless API roundtrips:
  • order
  • order.market
  • order.line_items
  • order.line_items.item
  • order.shipping_address
  • order.billing_address
  • order.customer
{
"data": {
...
},
"included": [
{
"id": "wBXVhKzrnq",
"type": "orders",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
{
"id": "DvlGRmhdgX",
"type": "markets",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
{
"id": "kdPgtRXOKL",
"type": "line_items",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
{
"id": "XGZwpOSrWL",
"type": "skus",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
}
{
"id": "BgnguJvXmb",
"type": "addresses",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
{ ... }
]
}

Authorization

When you place an order, Commerce Layer triggers a POST request to the endpoint that you specified in the authorize_url field and creates an authorization.

Example

Payload
Response
Error
The request payload contains the external payment resource and includes the above-mentioned relationships:
{
"data": {
"id": "ZNKjeUYepv",
"type": "external_payments",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
"included": [
{ ... }
]
}
The successful response must be a JSON object, returning a transaction token (e.g. the one provided by the payment gateway) and the total amount that has been authorized. If needed, you can add some metadata that will be copied into the authorization resource that is being created:
{
"success": true,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"metadata": {
"foo": "bar"
}
}
}
On error, you must respond with an HTTP code >= 400. The response body must be a JSON object containing a transaction token (e.g. the one provided by the payment gateway) and the authorization amount, along with any other relevant error code and message:
{
"success": false,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"error": {
"code": "YOUR-ERROR-CODE",
"message": "Your error message"
}
}
}

Capture

When you try to capture an authorization, Commerce Layer triggers a POST request to the endpoint that you specified in the capture_url field and creates a capture.

Example

Payload
Response
Error
The request payload contains the authorization resource and includes the above-mentioned relationships:
{
"data": {
"id": "yGzeUJxRJj",
"type": "authorizations",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
"included": [
{ ... }
]
}
The successful response must be a JSON object, returning a transaction token (e.g. the one provided by the payment gateway) and the total amount that has been captured. If needed, you can add some metadata that will be copied into the capture resource that is being created:
{
"success": true,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"metadata": {
"foo": "bar"
}
}
}
On error, you must respond with an HTTP code >= 400. The response must be a JSON object containing a transaction token (e.g. the one provided by the payment gateway) and the capture amount, along with any other relevant error code and message:
{
"success": false,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"error": {
"code": "YOUR-ERROR-CODE",
"message": "Your error message"
}
}
}

Void

When you try to void an authorization, Commerce Layer triggers a POST request to the endpoint that you specified in the void_url field and creates a void.

Example

Payload
Response
Error
The request payload contains the authorization resource and includes the above-mentioned relationships:
{
"data": {
"id": "yGzeUJxRJj",
"type": "authorizations",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
"included": [
{ ... }
]
}
The successful response must be a JSON object, returning a transaction token (e.g. the one provided by the payment gateway) and the total amount that has been voided. If needed, you can add some metadata that will be copied into the void resource that is being created:
{
"success": true,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"metadata": {
"foo": "bar"
}
}
}
On error, you must respond with an HTTP code >= 400. The response must be a JSON object containing a transaction token (e.g. the one provided by the payment gateway) and the void amount, along with any other relevant error code and message:
{
"success": false,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"error": {
"code": "YOUR-ERROR-CODE",
"message": "Your error message"
}
}
}

Refund

When you try to void a capture, Commerce Layer triggers a POST request to the endpoint that you specified in the refund_url field and creates a refund.

Example

Payload
Response
Error
The request payload contains the capture resource and includes the above-mentioned relationships:
{
"data": {
"id": "yJQDUVndWj",
"type": "captures",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
"included": [
{ ... }
]
}
The successful response must be a JSON object, returning a transaction token (e.g. the one provided by the payment gateway) and the amount that has been refunded. If needed, you can add some metadata that will be copied into the refund resource that is being created:
{
"success": true,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 9900,
"metadata": {
"foo": "bar"
}
}
}
On error, you must respond with an HTTP code >= 400. The response must be a JSON object containing a transaction token (e.g. the one provided by the payment gateway) and the refund amount, along with any other relevant error code and message:
{
"success": false,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 9900,
"error": {
"code": "YOUR-ERROR-CODE",
"message": "Your error message"
}
}
}

Customer token

When you try to store a payment token for a customer, Commerce Layer triggers a POST request to the endpoint that you specified in the token_url field and creates a customer payment source for the specified payment.

Example

Payload
Response
Error
The request payload contains the payment source resource and includes the above-mentioned relationships:
{
"data": {
"id": "GBNMKjUkry",
"type": "external_payments",
"links": { ... },
"attributes": { ... },
"relationships": { ... },
"meta": { ... }
},
"included": [
{ ... }
]
}
The successful response must be a JSON object, returning an optional customer_token (if missing the customer.email is used) and the payment_source_token that represents the saved payment for the customer:
{
"success": true,
"data": {
"customer_token": "your-external-customer-token",
"payment_source_token": "your-external-payment-source-token"
}
}
On error, you must respond with an HTTP code >= 400. The response must be a JSON object containing other relevant error code and message:
{
"success": false,
"data": {
"error": {
"code": "YOUR-ERROR-CODE",
"message": "Your error message"
}
}
}

Asynchronous payments

It might be the case you don't want your gateway to process payments immediately. That's why Commerce Layer provides the option to mark your external gateway response as asynchronous and expose a webhook_endpoint_url you can call once the payment status changes.
The token_url doesn't support asynchronous execution.

Action ID

A payment is marked as asynchronous when the following conditions on the response to any of the external payment gateway transactions are met:
  • HTTP code is 202
  • It contains the action_id key, which uniquely identifies the related transaction
action_id uniqueness is mandatory for the webhook to detect the transaction later.
In this case, the external payment gateway creates the transaction setting the succeeded attribute to false, but considering it as pending. This way, the order can be placed without errors, but the order payment status doesn't change yet (even if the order is not editable anymore).

Example

Payload
Response
Error
The payload requested by the related transaction, as explained in the authorization, capture, void, and refund sections.
The successful response must be a JSON object, returning a transaction token (e.g. the one provided by the payment gateway), the amount involved, and the unique identifier of the transaction. If needed, you can add some metadata that will be copied into the related transaction resource that is being created:
{
"success": true,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"action_id": "your-action-id"
"metadata": {
"foo": "bar"
}
}
}
On error, you must respond with an HTTP code >= 400. The response must be a JSON object containing a transaction token (e.g. the one provided by the payment gateway) and the amount involved in the transaction, along with any other relevant error code and messagee:
{
"success": false,
"data": {
"transaction_token": "your-external-transaction-token",
"amount_cents": 12900,
"error": {
"code": "YOUR-ERROR-CODE",
"message": "Your error message"
}
}
}

Webhook endpoint

To notify the payment has changed its status, the external gateway exposes a webhook_endpoint_url you can call accordingly once the related payment transaction gets an update, as long as you follow these requirements:
  • It accepts only POST requests
  • You must include an X-CommerceLayer-Signature header, which contains the HMAC of the request payload signed with a SHA256 algorithm and the same shared secret already exposed by the external payment gateway
  • The request body must have the same structure as the response — a JSON object with the attributes you need to update the transaction with — and include the action_id previously used
The external payment gateway will use this data to fetch the pending transaction and update the attributes with the new values. On successful update, the transaction succeeded attribute is set to true and the order is updated to the right status — authorized, paid, voided, or refunded. On error, the order status remains as it is.

Updatable attributes

Only a subset of attributes is allowed for an update, assuming the main ones have already been set by the first async response (e.g. amount_cents and transaction_token cannot be updated). The updatable transaction fields are:
  • message
  • error_code
  • error_detail
  • avs_code
  • avs_message
  • cvv_code
  • cvv_message
  • fraud_review

Security

When you create a new external payment gateway, a shared secret is generated. We recommend verifying the callback authenticity by signing the payload with that shared secret and comparing the result with the callback signature header.