Other Uses of PaymentWebShop

Introduction    Implementing    Other Uses     Parts

• Additional Payment Gateway Events

• Protect Events with RepeatedEventDetection

• More than one Payment Gateway Event per Page
   

Additional Payment Gateway Events

By default a Websydian PaymentWebShop implementation supports one event sent to the payment gateway, the Web.Ordering.Submit Payment.Ok event.

If more events are to be sent to the Payment Gateway, the page generator with the sending event and the sending event must be modified

Example

If the Submit Payment document itself must be relayed through the Payment Gateway, a few triples must be added.

First, the event handler initiating the Submit Payment document must be declared as a SendToExternalServer function, and its page generator must be declared as a PageGeneratorWithExternalEvent:

Second, a field for the payment gateway URL that relays the Submit Payment document must be added to the Shop entity and made available to the page generator: 

Last, an event handler to receive the Submit Payment Form request from the payment gateway must be added. Since it must do the same processing as the Enter Contact Information.OK event handler, it is obvious to let it inherit from this function:

Now the PaymentWebShop implementation will load its Submit Payment document relayed through the payment gateway.

Protect Events with RepeatedEventDetection

It is strongly recommended that events sent to a payment gateway should be protected against accidental repeat e.g. because a web user hits the "Submit payment" button more than once while waiting for the payment confirmation.

The Websydian pattern Repeated Event Detection can be used to protect payment gateway events.

Example

The Submit Payment.OK event should be protected against accidental repeat. Both the scoped OK event handler and the event handlers receiving the result from the payment gateway must be modified:

This will add a PageID field to the Submit Payment.OK event. In order for the  RepeatedEventDetection implementation to work, the payment gateway must relay event parameters not part of the payment gateway protocol unchanged.

Refer to the Repeated Event Detection pattern documentation for more information.

More than one Payment Gateway Event per Page 

The abstract PaymentGateway entity in PaymentWebShop is based on the pattern WSYUTIL/ExternalServerControl. This pattern is based on the assumption that a WebShop document has one and only one external event, and that the external URL is given by a field present in WsyDetails derived from the ancestor-field ExternalServerControl.Fields.URLString.

If a PaymentWebShop document should hold more than one payment gateway event, the page must be divided into one parent page and several child pages by using the Parent Child Page Generator pattern.