I have implemented 2 payment gateways in my app (paypal and datatrans). In both gateways payment happens on gateway site i.e. user is redirected to payment gateway site where he pays and then redirected back to our site.
I have identified some scenarios where there is some issue in entire payment flow. E.g.
- lost internet connection after payment and so order is not placed but money got debited from user’s account
- PayPal sent response but application got exception and so user did not get confirmation
- Double payment due to hitting refresh button when transaction was in progress
I would like to know what are standard exceptions should be handled in payment gateway integration.
Any example with paypal would help me lot, I use asp.net mvc 3. thanks.
Double payment.
To avoid them you need to create a unique ID for every order, after the user move from your site to the paypal or other site, this ID must be read-only, and if the user return to your site after fail or other reason, and ask to re-order the same cart, you must create a new cart, and a new order ID.
For every order id, paypal and other sites allow only one payment (or one fail).
Lost the internet connections, or not get confirmations
Paypal have 3 ways that contact with your.
The one is that you get information from the return of the user after the payment, the other method is that paypal communicate with you and send you the payment informations, and final you get email.
In the rare case that all fails, user will inform you after some days that he did not get his order.
Practical they never fail all of them. Actually they never fail any of them.
Exceptions and bugs
Well some times you can not avoid bugs, so monitor your payments and log any possible errors to fix it. After 7 years of payments with paypal I still monitor them for problems, fraud, issues, new thinks etc, and still make some small adjustments time to time.