Project 4: E-Commerce Microservice System

Assume eureka-server and product-service are running and registered in Eureka.

1. The Feign Client (in order-service)

package com.devinhyderabad;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

// 1. Feign will look up PRODUCT-SERVICE in Eureka
@FeignClient(name = "PRODUCT-SERVICE")
public interface ProductClient {
    
    // Calls the endpoint in the product-service
    @GetMapping("/api/products/{id}/stock")
    Boolean checkStock(@PathVariable Long id);
}

2. The Order Service with Circuit Breaker (OrderService.java)

package com.devinhyderabad;

import io.github.resilience4j.circuitbreaker.annotation.CircuitBreaker;
import org.springframework.stereotype.Service;

@Service
public class OrderService {

    private final ProductClient productClient;

    public OrderService(ProductClient productClient) {
        this.productClient = productClient;
    }

    // 1. If this method fails 3 times, the circuit opens
    @CircuitBreaker(name = "productServiceCB", fallbackMethod = "handleProductServiceDown")
    public String placeOrder(Long productId) {
        // 2. Feign calls the Product Microservice
        Boolean inStock = productClient.checkStock(productId);

        if (inStock) {
            return "Order placed successfully!";
        } else {
            return "Product is out of stock.";
        }
    }

    // 3. Fallback executed if product-service is down or circuit is open
    public String handleProductServiceDown(Long productId, Exception e) {
        return "Our inventory system is currently unavailable. Please try again later. (Fallback)";
    }
}

3. The Order Controller (OrderController.java)

package com.devinhyderabad;

import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/api/orders")
public class OrderController {
    private final OrderService orderService;

    public OrderController(OrderService orderService) {
        this.orderService = orderService;
    }

    @PostMapping("/{productId}")
    public String createOrder(@PathVariable Long productId) {
        return orderService.placeOrder(productId);
    }
}