Project: E-commerce Microservice Architecture

We will design a system with two services: Product Service and Order Service.

Architecture

• Eureka Server: Service Discovery.
• Product Service: Manages inventory.
• Order Service: Places orders and communicates with Product Service.
• API Gateway: Entry point.

1. Product Service

ProductController

@GetMapping("/{id}")
public Product getProduct(@PathVariable Long id) {
    return repository.findById(id).orElseThrow();
}

2. Order Service

Needs to call Product Service to check availability/price.

Feign Client

Declarative REST client.

@FeignClient(name = "product-service")
public interface ProductClient {
    @GetMapping("/products/{id}")
    ProductDTO getProduct(@PathVariable Long id);
}

OrderService

@Service
public class OrderService {
    @Autowired
    private ProductClient productClient;
    
    public Order placeOrder(Long productId, int quantity) {
        // Call Product Service
        ProductDTO product = productClient.getProduct(productId);
        
        // Logic
        Order order = new Order();
        order.setProductId(productId);
        order.setAmount(product.getPrice() * quantity);
        return repository.save(order);
    }
}

3. Communication

Using Spring Cloud OpenFeign allows services to talk to each other like calling a local method.

4. Resilience

Add Resilience4j Circuit Breaker if Product Service is down.

@CircuitBreaker(name = "productService", fallbackMethod = "fallbackProduct")
public ProductDTO getProduct(Long id) {
    return productClient.getProduct(id);
}

public ProductDTO fallbackProduct(Long id, Throwable t) {
    return new ProductDTO(id, "Default Product", 0.0);
}

Quiz