Spring Cloud

Language: Java

Microservices / Cloud

Spring Cloud was developed to simplify the development of microservices and distributed systems in the Spring ecosystem. It abstracts common challenges such as service registration, configuration synchronization, messaging, and resiliency. Widely adopted in enterprise applications, Spring Cloud allows developers to quickly build scalable, fault-tolerant microservices on cloud platforms.

Spring Cloud provides a suite of tools for building distributed systems and microservices in Java. It integrates with Spring Boot to offer service discovery, configuration management, load balancing, circuit breakers, messaging, and cloud-native patterns.

Installation

maven:

Add dependencies in pom.xml:
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
  <version>3.1.6</version>
</dependency>
<dependency>
  <groupId>org.springframework.cloud</groupId>
  <artifactId>spring-cloud-starter-config</artifactId>
  <version>3.1.6</version>
</dependency>

gradle:

implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client:3.1.6'
implementation 'org.springframework.cloud:spring-cloud-starter-config:3.1.6'

Usage

Spring Cloud provides tools for service discovery (Eureka), configuration management (Spring Cloud Config), distributed messaging (Spring Cloud Stream), API gateway (Spring Cloud Gateway), load balancing (Ribbon), and resiliency (Hystrix / Resilience4j).

Eureka Client Registration

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

Registers a Spring Boot application as a Eureka client for service discovery.

Fetching configuration from Spring Cloud Config

@RefreshScope
@RestController
public class ConfigController {
    @Value("${example.property}")
    private String property;

    @GetMapping("/property")
    public String getProperty() {
        return property;
    }
}

Reads properties from a centralized Spring Cloud Config server and exposes them via a REST endpoint.

Load-balanced RestTemplate

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

String response = restTemplate.getForObject("http://my-service/endpoint", String.class);

Uses service names instead of hard-coded URLs, with automatic client-side load balancing via Ribbon.

Circuit breaker with Resilience4j

@RestController
public class MyController {
    @Autowired
    private SomeService service;

    @GetMapping("/call")
    @CircuitBreaker(name = "backendService", fallbackMethod = "fallback")
    public String callService() {
        return service.call();
    }

    public String fallback(Throwable t) {
        return "Fallback response";
    }
}

Implements a circuit breaker pattern to gracefully handle service failures.

Spring Cloud Gateway route

@Bean
public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
    return builder.routes()
        .route("path_route", r -> r.path("/get")
            .uri("http://httpbin.org"))
        .build();
}

Configures an API gateway route to forward requests to another service.

Spring Cloud Stream with Kafka

@EnableBinding(Sink.class)
public class MyStreamListener {
    @StreamListener(Sink.INPUT)
    public void handle(String message) {
        System.out.println("Received: " + message);
    }
}

Consumes messages from a messaging broker using Spring Cloud Stream abstraction.

Error Handling

ServiceUnavailableException: Occurs when a service cannot be discovered. Ensure Eureka server is running and services are registered.

Configuration refresh not applied: Use /actuator/refresh endpoint or @RefreshScope to reload updated properties from Config Server.

CircuitBreakerOpenException: Thrown when circuit breaker is open. Check service availability and fallback methods.

Best Practices

Use Spring Cloud Config for centralized configuration and environment management.

Leverage service discovery (Eureka, Consul) for dynamic routing.

Implement circuit breakers and retries for resiliency.

Use Spring Cloud Gateway for routing and API management.

Monitor and log distributed systems with Sleuth, Zipkin, or Micrometer.

Official Docs Github