Java 開発におけるマイクロサービス アーキテクチャのベスト プラクティス

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

@Entity
@Table(name = "orders")
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String orderNumber;
    // ...其他属性和方法
}

@Repository
public interface OrderRepository extends JpaRepository<Order, Long> {
    // ...其他方法
}

@RestController
@RequestMapping("/orders")
public class OrderController {
    private final OrderRepository orderRepository;

    public OrderController(OrderRepository orderRepository) {
        this.orderRepository = orderRepository;
    }

    @PostMapping
    public Order createOrder(@RequestBody Order order) {
        return orderRepository.save(order);
    }

    @GetMapping("/{id}")
    public Order getOrder(@PathVariable Long id) {
        return orderRepository.findById(id)
                            .orElseThrow(() -> new RuntimeException("Order not found"));
    }
}

spring:
  application:
    name: order-service
  cloud:
    discovery:
      register-with-eureka: true
      fetch-registry: true
      service-url:
        defaultZone: http://localhost:8761/eureka

server:
  port: 8081

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

@FeignClient(name = "user-service")
public interface UserClient {
    @GetMapping("/users/{id}")
    User getUser(@PathVariable Long id);
}

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

@RestController
@RequestMapping("/orders")
public class OrderController {
    private final OrderRepository orderRepository;
    private final UserClient userClient;
    private final ProductClient productClient;

    public OrderController(OrderRepository orderRepository, 
                           UserClient userClient, 
                           ProductClient productClient) {
        this.orderRepository = orderRepository;
        this.userClient = userClient;
        this.productClient = productClient;
    }

    @PostMapping
    public Order createOrder(@RequestBody Order order) {
        User user = userClient.getUser(order.getUserId());
        Product product = productClient.getProduct(order.getProductId());

        // ...处理订单逻辑
        return orderRepository.save(order);
    }

    // ...其他方法
}