SmartPark

A REST API for managing parking lots and vehicles, built with Spring Boot. Supports JWT-based authentication, parking check-in/check-out with automatic cost calculation, and a scheduled job that auto-removes vehicles parked longer than 15 minutes.

Tech Stack

• Java 26
• Spring Boot 4.0.6 (Web MVC, Data JPA, Security, Validation)
• H2 in-memory database
• JJWT 0.12.5 for token signing/verification
• JUnit 5 + Mockito for testing (via Spring Boot's modular test starters)
• Maven build

Prerequisites

• JDK 17 or higher
• Maven 3.6+ (or use the included ./mvnw wrapper — no install needed)

Build & Run

Clone the repo, then from the project root:

# Build
./mvnw clean install

# Run
./mvnw spring-boot:run

The app starts on http://localhost:8080.

H2 console (for inspecting the in-memory DB) is available at http://localhost:8080/h2-console:

• JDBC URL: jdbc:h2:mem:smartparkdb
• Username: sa
• Password: (empty)

Run Tests

./mvnw test

Authentication

All endpoints except /api/auth/login require a JWT bearer token.

Static credentials (configurable via env vars):

• Username: admin
• Password: admin123

To override: set APP_AUTH_USERNAME, APP_AUTH_PASSWORD, and JWT_SECRET environment variables. Defaults are baked in for ease of evaluation; in production, secrets would be injected via environment variables or a secrets manager and never committed.

Get a token:

curl -X POST http://localhost:8080/api/auth/login \
  -H "Content-Type: application/json" \
  -d '{"username":"admin","password":"admin123"}'

Then include it on subsequent requests:

curl http://localhost:8080/api/lots -H "Authorization: Bearer <token>"

Tokens expire after 1 hour by default.

API Endpoints

Method	Path	Description
POST	/api/auth/login	Login, returns JWT
POST	/api/lots	Register a parking lot
GET	/api/lots	List all parking lots
GET	/api/lots/{lotId}	Get a parking lot (includes occupancy/availability)
POST	/api/vehicles	Register a vehicle
GET	/api/vehicles	List all vehicles
GET	/api/vehicles/{licensePlate}	Get a vehicle
POST	/api/parking/check-in	Check a vehicle into a lot
POST	/api/parking/check-out	Check a vehicle out, returns cost
GET	/api/parking/lots/{lotId}/vehicles	List vehicles currently parked in a lot

Postman Collection

A Postman collection with all endpoints is included at postman/SmartPark.postman_collection.json.

To use it:

1. Import the file into Postman (Import → select the file)
2. Run the Login request first — it auto-populates the token collection variable
3. Run any other request; auth is inherited from the collection

Preloaded Data

On startup, data.sql seeds:

• 4 parking lots (LOT-001 through LOT-004)
• 5 vehicles (ABC-1234, XYZ-9876, MOT-0001, TRK-5555, CAR-2222)

This lets you exercise the check-in / check-out flow immediately without registering anything new.

Business Rules

• Lot capacity is enforced. Check-in fails with HTTP 409 if the lot is full.
• A vehicle can only be parked in one lot at a time. Check-in fails with HTTP 409 if the vehicle has an active session.
• Occupancy updates automatically on check-in (increment) and check-out (decrement).
• Cost is calculated on checkout based on costPerMinute × minutes parked. Partial minutes are rounded up — a 15-second stay still costs 1 minute. The final cost is rounded to 2 decimal places.
• Auto-checkout for vehicles parked over 15 minutes. A scheduled job runs every 30 seconds, finds active sessions older than the threshold, and force-checks them out — calculating cost, freeing the space, and marking the session with autoCheckedOut: true. Threshold is configurable via app.parking.auto-checkout-minutes.

Design Notes & Assumptions

• ParkingSession is a separate entity tracking each check-in/check-out as a record. It's not in the spec explicitly, but it's needed to track timestamps, cost, and the active/inactive state cleanly.
• BigDecimal is used for all monetary values (costPerMinute, cost) to avoid floating-point precision issues. Rates use scale 4 (per-minute pricing may be sub-cent); final costs are rounded to scale 2.
• The "view occupancy and availability" requirement is satisfied by GET /api/lots/{lotId} — the response includes capacity, occupiedSpaces, and availableSpaces. A separate endpoint would just return a subset of the same data.
• Auto-checkout interpreted literally: at 15 minutes, the vehicle is force-removed and the customer is charged for the time used. If the spec intended a different behavior (e.g., a free grace period), this can be adjusted by changing ParkingService.autoCheckOut().
• HTTP 409 (Conflict) is used for state-conflict errors (lot full, already parked) to distinguish them from input-validation errors (HTTP 400).
• No controller tests, only service tests. Controllers in this app are thin pass-throughs; the business rules under test live in the service layer. Service-level testing covers the spec's requirements without testing Spring's plumbing.

Project Structure

src/main/java/com/smartpark/
├── SmartParkApplication.java       # Main entry point with @EnableScheduling
├── config/                          # (reserved for future use)
├── controller/                      # REST endpoints
├── dto/                             # Request and response objects
├── entity/                          # JPA entities
├── exception/                       # Global exception handler
├── repository/                      # Spring Data JPA repositories
├── scheduler/                       # Auto-checkout scheduled job
├── security/                        # JWT service, auth filter, security config
└── service/                         # Business logic

src/main/resources/
├── application.properties           # Config
└── data.sql                         # Preloaded reference data

src/test/java/com/smartpark/
└── service/                         # Service layer unit tests

postman/
└── SmartPark.postman_collection.json

Configuration Reference

Defaults in application.properties. Override via environment variables.

Property	Default	Description
server.port	8080	HTTP port
app.jwt.secret	(base64-encoded demo key)	HMAC signing key for JWTs
app.jwt.expiration-ms	3600000 (1 hour)	Token lifetime
app.auth.username	admin	Login username
app.auth.password	admin123	Login password
app.parking.auto-checkout-minutes	15	Threshold for auto-checkout
app.parking.scheduler-rate-ms	30000 (30s)	Scheduler frequency