Mar 17, 2019 · PayPal Java SDK Complete Example – How to Invoke PayPal Authorization REST API using Java Client? Last Updated on March 17th, 2019 by App Shah 16 comments PayPal is one of the best online Payment transfer service out there. When a payment notification is received from PayPal, WHMCS makes an API request to PayPal confirming that the notification originated from PayPal. Seeing this typically indicates that a subscription renewal payment was made through a different integration app from the one currently linked to your WHMCS installation.
PayPal’s NVP API makes it simple to integrate payments into your application. As the merchant, your web application constructs an NVP string and transmit it via HTTPS (HTTP Secure) to the PayPal authorization server, and PayPal sends back an NVP-formatted response that your web application parses for the information relevant to the payment.