FreeSignup API (Spring)

Complete a signup API built on Spring Boot 3 and JPA (in-memory H2) that registers users by email and password. It takes a signup request, stores it, and returns the registered user with a 201. The controller handles only the HTTP boundary while the signup logic lives in the service.

An API like signup that takes data sent by a client and stores it centers on how incoming input is received and handled at the server boundary. A request can reach the server directly without going through a screen, so the server boundary becomes the first point at which input is handled. This problem practices the flow of receiving incoming sign-up data through to storing it.

In Spring, where does signup logic belong — the controller or the service?

The controller handles only the HTTP request/response boundary, while business rules such as signup live in the service layer. Domain errors are thrown in the service and mapped to HTTP statuses in the controller.

How do you verify a signup API?

Beyond the path where a normal input succeeds and returns 201, it's good to also check how the server handles the various shapes of input that can arrive at it.