ERP Starter — Spec Kit Workshop Starter Repo

A tiny plain-Java / Maven / JUnit project used as the brownfield starter for a GitHub Spec Kit workshop.

This is a brownfield starter: the repo already ships with three modules (Customer, Article, Order) wired into a small CLI, following a consistent pattern. The workshop exercise is to add a Supplier module using the same pattern, but driven through the Spec Kit workflow rather than jumping straight into code.

See LAB.html for the workshop script (open it in a browser).

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Prerequisites

• JDK 17+
• Maven 3.9+ (or use your IDE's embedded one)
• Any IDE (Eclipse, IntelliJ, VS Code — it's a standard Maven project)
• GitHub Copilot CLI with Spec Kit

Build & run

mvn test                 # runs the existing JUnit tests (should be green)
mvn package              # builds target/erp-starter.jar
java -jar target/erp-starter.jar

You should land in this CLI:

=== ERP Starter ===
 1) Customers
 2) Articles
 3) Orders
 q) Quit
>

What is already implemented

com.example.erp
├── ErpApp              main() + top-level CLI menu
├── DataSeeder          seeds the in-memory repos on startup
├── common
│   ├── Cli             tiny stdin helper
│   └── RuleException   thrown by service-level rule failures
├── customer
│   ├── Customer, CustomerContact
│   ├── CustomerRepository  (+ InMemoryCustomerRepository)
│   ├── CustomerService     ← note beforeSave / beforeDeactivate hooks
│   ├── CustomerListReport
│   ├── CustomerCli
│   └── rules/VatValidator
├── article
│   ├── Article, ArticleRepository, InMemoryArticleRepository
│   ├── ArticleService
│   └── ArticleCli
└── order
    ├── Order, OrderStatus
    ├── OrderRepository (+ InMemoryOrderRepository)
    └── OrderCli

All three existing modules share the same shape:

• a model (POJO + optional child records)
• a repository interface with an in-memory implementation
• a service with explicit beforeSave / beforeDeactivate hooks for business rules
• optional rules classes (pure, JUnit-tested) — validation logic
• a CLI for the user

Note on the Order module

Order is deliberately read-only in this starter. Its repository is what the future SupplierService.beforeDeactivate rule must consult to check whether a supplier has open orders. It's included so that rule has something real to talk to.

Repo shape (excerpt)

.
├── pom.xml
├── README.md
├── LAB.html
├── src/main/java/com/example/erp/…
└── src/test/java/com/example/erp/…