External services¶
An onboarding decision may need an identity check from another service. After acceptance, the applicant may need a confirmation. Treat each provider call as a separate boundary with its own credentials, failure policy, and observable outcome.
Add one integration for one need¶
| Onboarding need | Smallest useful starting point |
|---|---|
| Call a remote API | Client, using the protocol that API supports |
| Send an email, SMS, or push notification | One notification provider and its channel service |
| Deliver subscribed events to partner HTTP endpoints | Callbacks |
| Invoke a remote Agentic runtime | Agentic bridge core, or its starter for Spring wiring |
These are extensions to the onboarding application. The first-service and event-store examples run without those providers.
Follow a provider call¶
Start with the client guide. Identify the actual request and response contract, then select REST, SOAP, or gRPC. Set a timeout and decide whether the operation can safely repeat before enabling a retry policy.
The complete client example contains concrete protocol helpers in a standalone application. Its configuration belongs to that project. Read the required service settings before running it; a successful compilation does not establish access to a real provider.
The REST integration test shows controlled requests and responses. Test your provider's timeout, error response, and duplicate-request behavior separately. SOAP and gRPC do not automatically inherit every REST retry or circuit-breaker policy.
Send a confirmation¶
For email, choose a provider such as SendGrid or Resend. Their adapters bring the core contracts transitively. Follow the notification setup to configure the provider and explicitly register the channel service before injecting it.
Keep credentials in deployment configuration. Check the provider response and any later delivery status that the application needs. A successful method invocation is not proof that a message reached the applicant's inbox.
Use callbacks for outbound partner subscriptions and webhooks for inbound provider notifications. They solve different directions of communication. Agentic integration also needs its separate runtime and endpoint configuration.
If a direct Spring WebClient call already meets a small integration's needs, adopting a larger provider platform is optional.
Next, consider event-driven integration when another operation should react asynchronously to the onboarding result.