Boundary Examples

Example applications built with the Boundary Framework. Each example is a self-contained Clojure project demonstrating the Functional Core / Imperative Shell (FC/IS) architecture pattern.

Prerequisites

• Java 11+
• Clojure CLI
• Babashka (optional, for root-level tasks)

Examples

Example	Complexity	Port	Description
blog-app	⭐⭐ Intermediate	3001	Server-rendered blog with HTMX and SQLite
ecommerce-api	⭐⭐⭐ Advanced	3002	REST API with cart, orders, and mock Stripe payments
notification-service	⭐⭐ Intermediate	3003	Event-driven pub/sub notification microservice

---

Blog App

A full-stack blog with HTMX-powered UI and SQLite persistence.

cd blog-app
clojure -M:run

Open http://localhost:3001. Go to /dashboard to create posts.

Run tests:

clojure -M:test

---

E-commerce API

A JSON REST API with products, a session-based cart, order state machine, and mock Stripe payment integration. Includes a boundary-admin UI for managing products, orders, and users.

cd ecommerce-api
clojure -M:run

API available at http://localhost:3002/api.

Create an admin user (required for the admin UI at /web/admin/):

# From the repo root
bb create-admin --dir ecommerce-api

Simulate a purchase:

# Add a product to the cart
curl -X POST http://localhost:3002/api/cart/items \
  -H "Content-Type: application/json" \
  -H "X-Session-ID: demo" \
  -d '{"product-id": "11111111-1111-1111-1111-111111111111", "quantity": 1}'

# Checkout
ORDER=$(curl -s -X POST http://localhost:3002/api/checkout \
  -H "Content-Type: application/json" \
  -H "X-Session-ID: demo" \
  -d '{"email":"demo@example.com","name":"Demo","shipping-address":{"line1":"123 Main St","city":"Amsterdam","postal-code":"1234AB","country":"NL"}}')
ORDER_ID=$(echo $ORDER | python3 -c "import sys,json; print(json.load(sys.stdin)['data']['id'])")

# Simulate payment success
curl -X POST http://localhost:3002/api/payments/simulate \
  -H "Content-Type: application/json" \
  -d "{\"order-id\": \"$ORDER_ID\", \"success\": true}"

Run tests:

clojure -M:test

---

Notification Service

An event-driven microservice that listens for domain events (orders, payments, shipments) over an in-memory pub/sub bus and dispatches mock email/SMS/push notifications with exponential-backoff retry.

cd notification-service
clojure -M:run

Publish an event:

curl -X POST http://localhost:3003/api/events \
  -H "Content-Type: application/json" \
  -d '{
    "type": "order/placed",
    "payload": {
      "order-number": "ORD-001",
      "customer-name": "Jane Smith",
      "customer-email": "jane@example.com",
      "total-cents": 4999,
      "currency": "EUR"
    }
  }'

Check delivered notifications:

curl http://localhost:3003/api/notifications

Run tests:

clojure -M:test

---

Running All Tests

From the repo root (requires Babashka):

bb test-all

Architecture

All examples follow the same module structure:

<module>/
├── schema.clj        # Malli validation schemas
├── ports.clj         # Protocol (interface) definitions
├── core/<thing>.clj  # Pure business logic — no I/O, no side effects
└── shell/
    ├── persistence.clj  # Database adapter
    ├── service.clj      # Orchestration layer
    └── http.clj         # HTTP handlers

The core contains only pure functions — easy to test without mocks. The shell wires them together with databases, HTTP, and other external services. Ports (defprotocol) define the boundary between the two, making adapters swappable.

REPL Development

Each app exposes an nREPL server via clojure -M:repl-clj:

App	nREPL port
blog-app	7889
ecommerce-api	7890
notification-service	7891

From the REPL:

(require '[<app>.system :as sys])
(def system (sys/start!))
;; make changes, then reload namespaces and restart as needed
(sys/stop! system)