Payment Stub

Your project also integrates with the payment stub - a stateless stand-in for a 3rd-party payment provider, published as a pre-built Docker image. Setup is identical to the JSP track: follow Step 10: Set Up the Payment Stub for authenticating to GHCR (if needed), pulling and running the image (standalone or as a service in your docker-compose.yml), the /quote and /payments endpoints, the available configuration, and a Java client you can adapt for your API tier.

Note

You’ll need Docker for this, set up in Milestone 1: Deployment. Otherwise this can be done at any point - it doesn’t depend on the other milestones.

React-specific notes

• Call it from your API, not the browser. The React SPA talks to your Servlet API; the Servlet API talks to the payment stub. Calling the stub directly from the browser would expose the SHARED_SECRET (if you set one) and put a third-party dependency directly in the client.

• The UI needs a pending state. Every stub response takes 3-8 seconds by design. Disable the submit control and show a spinner while the request is in flight, using the same Hooks-based async patterns covered in Milestone 2: Core functionality.

• Give REJECTED and a 5xx different UX. A REJECTED response is a clean decline - show it as a normal validation-style message. A 5xx is a transient failure - show it as a retryable error, not a declined payment.