🚀 Microservices Backend (Java/Spring)

This repository contains a small microservices system wired through an API Gateway. Each service runs as a Spring Boot application with H2 in-memory databases for local development.

🧩 Services and Ports

• 🧭 Service Registry (Eureka): service-registry → http://localhost:8761
• 🛡️ API Gateway (Spring Cloud Gateway MVC): api-gateway → http://localhost:8080
• 📦 Product Service: product-service → http://localhost:8081
• 🧾 Order Service: order-service → http://localhost:8082
• 👤 User/Auth Service: user-service → http://localhost:8083
• ⚙️ Config Server: config-server (disabled by default: spring.cloud.config.enabled: false)

📋 Prerequisites

• ☕ Java 17+
• 🧰 Maven 3.9+
• 🐳 (Optional) Docker for Kafka if you want to run Kafka locally

▶️ Running Locally

You can run in two modes. The repository is currently configured to use Direct URIs in the gateway for simplicity.

A) 🔗 Direct-URI Mode (no Eureka)

1. Start services in any order:
   • product-service (8081)
   • order-service (8082)
   • user-service (8083)
2. Start api-gateway (8080)
3. Visit http://localhost:8080/...

Gateway routes are configured in api-gateway/src/main/resources/application.yml:

spring:
  cloud:
    gateway:
      server:
        webmvc:
          routes:
            - id: product-service
              uri: http://localhost:8081
              predicates:
                - Path=/products/**
            - id: order-service
              uri: http://localhost:8082
              predicates:
                - Path=/orders/**
            - id: user-service
              uri: http://localhost:8083
              predicates:
                - Path=/auth/**

B) 🛰️ Eureka Mode (load-balanced)

1. Start service-registry (8761)
2. Revert gateway URIs to lb://product-service, lb://order-service, lb://user-service
3. Start product-service, order-service, user-service (they register with Eureka)
4. Start api-gateway

🔐 Security and Auth

The gateway enforces JWT-based authentication for most routes, with the following exceptions configured in api-gateway SecurityConfig:

• ✅ Permit all: /auth/**
• ✅ Permit all: GET /products/**, GET /orders/** (for easier development)
• 🔒 Everything else: requires Authorization: Bearer <token>

Auth endpoints (proxied via gateway to user-service):

• POST /auth/register → body: { name, email, password, role }, role is USER or ADMIN
• POST /auth/login → body: { email, password } returns a JWT string

Include the token in calls to protected endpoints:

Authorization: Bearer <your_jwt>

📚 Core Endpoints

Product Service (via Gateway):

• GET /products → list products
• GET /products/{id} → product details
• POST /products → create product (requires JWT)
• PUT /products/{id} / DELETE /products/{id} → update/delete (requires JWT)

Order Service (via Gateway):

• GET /orders → list orders
• GET /orders/{id} → order details
• POST /orders → create order (requires JWT)
  • Body shape: { "orderItems": [{ "productId": number, "quantity": number }] }

User Service (via Gateway):

• POST /auth/register
• POST /auth/login

📡 Kafka (Stock Updates)

• Orders publish stock update events after creation.
• Product Service consumes and updates stock levels.
• If you see errors like "Product not found with id X" in product-service, create products first before placing orders.

🗄️ Local Databases

• Each service uses H2 in-memory DB by default (ddl-auto: update). Data resets on service restart.

🧯 Troubleshooting

• 503 "Unable to find instance for ...":
  • In Direct-URI mode: ensure target service is up (8081/8082/8083).
  • In Eureka mode: ensure service-registry is running and services have registered.
• 401/403 from gateway:
  • Obtain a JWT via POST /auth/login and include Authorization: Bearer <token>.
  • For quick dev, GET /products/** and GET /orders/** are already public.
• Kafka listener errors in product-service about missing product IDs:
  • Create product(s) first; then place orders using those IDs.

🛠️ Build

Run each service:

cd <service-folder>
./mvnw spring-boot:run

Or build jars:

./mvnw -DskipTests package

---

For the frontend, see frontend/ (React + Vite) – not covered in this README.