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

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }
}

server:
  port: 8761

eureka:
  client:
    register-with-eureka: false
    fetch-registry: false
  server:
    enable-self-preservation: false

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

@SpringBootApplication
@EnableDiscoveryClient
public class UserServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(UserServiceApplication.class, args);
    }
}

spring:
  application:
    name: user-service

server:
  port: 8081

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/
  instance:
    prefer-ip-address: true

user-service:
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RoundRobinRule
    ConnectTimeout: 3000
    ReadTimeout: 3000
    MaxAutoRetries: 1
    MaxAutoRetriesNextServer: 1

@Configuration
public class RestTemplateConfig {
    
    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

@Service
public class OrderService {
    
    @Autowired
    private RestTemplate restTemplate;
    
    public User getUserInfo(Long userId) {
        String url = "http://user-service/api/users/" + userId;
        return restTemplate.getForObject(url, User.class);
    }
}

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

@SpringBootApplication
@EnableDiscoveryClient
@EnableCircuitBreaker
public class OrderServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderServiceApplication.class, args);
    }
}

@Service
public class OrderService {
    
    @Autowired
    private RestTemplate restTemplate;
    
    @HystrixCommand(
        fallbackMethod = "getUserInfoFallback",
        commandProperties = {
            @HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "3000"),
            @HystrixProperty(name = "circuitBreaker.requestVolumeThreshold", value = "10"),
            @HystrixProperty(name = "circuitBreaker.errorThresholdPercentage", value = "50"),
            @HystrixProperty(name = "circuitBreaker.sleepWindowInMilliseconds", value = "10000")
        }
    )
    public User getUserInfo(Long userId) {
        String url = "http://user-service/api/users/" + userId;
        return restTemplate.getForObject(url, User.class);
    }
    
    public User getUserInfoFallback(Long userId) {
        // 폴백 로직: 기본값 반환 또는 캐시된 데이터 사용
        User fallbackUser = new User();
        fallbackUser.setId(userId);
        fallbackUser.setName("Unknown User");
        return fallbackUser;
    }
}

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

@SpringBootApplication
@EnableZuulProxy
@EnableDiscoveryClient
public class ApiGatewayApplication {
    public static void main(String[] args) {
        SpringApplication.run(ApiGatewayApplication.class, args);
    }
}

server:
  port: 8080

spring:
  application:
    name: api-gateway

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/

zuul:
  routes:
    user-service:
      path: /api/users/**
      serviceId: user-service
      stripPrefix: false
    order-service:
      path: /api/orders/**
      serviceId: order-service
      stripPrefix: false
  sensitive-headers: Cookie,Set-Cookie

@Component
public class AuthenticationFilter extends ZuulFilter {
    
    @Override
    public String filterType() {
        return "pre";
    }
    
    @Override
    public int filterOrder() {
        return 1;
    }
    
    @Override
    public boolean shouldFilter() {
        return true;
    }
    
    @Override
    public Object run() throws ZuulException {
        RequestContext ctx = RequestContext.getCurrentContext();
        HttpServletRequest request = ctx.getRequest();
        
        String token = request.getHeader("Authorization");
        
        if (token == null || !isValidToken(token)) {
            ctx.setSendZuulResponse(false);
            ctx.setResponseStatusCode(HttpStatus.UNAUTHORIZED.value());
            ctx.setResponseBody("Unauthorized");
            return null;
        }
        
        return null;
    }
    
    private boolean isValidToken(String token) {
        // JWT 토큰 검증 로직
        return true;
    }
}

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

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class OrderServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(OrderServiceApplication.class, args);
    }
}

@FeignClient(name = "user-service")
public interface UserServiceClient {
    
    @GetMapping("/api/users/{userId}")
    User getUserById(@PathVariable("userId") Long userId);
    
    @PostMapping("/api/users")
    User createUser(@RequestBody User user);
    
    @PutMapping("/api/users/{userId}")
    User updateUser(@PathVariable("userId") Long userId, @RequestBody User user);
    
    @DeleteMapping("/api/users/{userId}")
    void deleteUser(@PathVariable("userId") Long userId);
}

@Service
public class OrderService {
    
    @Autowired
    private UserServiceClient userServiceClient;
    
    public Order createOrder(Long userId, OrderRequest request) {
        // Feign을 통해 user-service 호출
        User user = userServiceClient.getUserById(userId);
        
        if (user == null) {
            throw new UserNotFoundException("User not found");
        }
        
        // 주문 생성 로직
        Order order = new Order();
        order.setUserId(userId);
        order.setUserName(user.getName());
        // ...
        
        return order;
    }
}

feign:
  client:
    config:
      default:
        connectTimeout: 5000
        readTimeout: 5000
      user-service:
        connectTimeout: 3000
        readTimeout: 3000

feign:
  hystrix:
    enabled: true

@FeignClient(name = "user-service", fallback = UserServiceClientFallback.class)
public interface UserServiceClient {
    @GetMapping("/api/users/{userId}")
    User getUserById(@PathVariable("userId") Long userId);
}

@Component
public class UserServiceClientFallback implements UserServiceClient {
    @Override
    public User getUserById(Long userId) {
        User fallbackUser = new User();
        fallbackUser.setId(userId);
        fallbackUser.setName("Unknown User");
        return fallbackUser;
    }
}

@Configuration
public class FeignConfig {
    
    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }
}

logging:
  level:
    com.example.client.UserServiceClient: DEBUG

ecommerce-microservices/
├── eureka-server/
│   ├── src/
│   └── pom.xml
├── api-gateway/
│   ├── src/
│   └── pom.xml
├── user-service/
│   ├── src/
│   └── pom.xml
├── product-service/
│   ├── src/
│   └── pom.xml
├── order-service/
│   ├── src/
│   └── pom.xml
├── payment-service/
│   ├── src/
│   └── pom.xml
└── pom.xml (parent)

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Hoxton.SR12</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>