Spring Cloud Config & Discovery Dependencies

Introduction

A microservices system might have dozens of services, each needing configuration and each needing to find the others at runtime. Spring Cloud provides two dependency pairs to solve this: Config Server/Client for centralized configuration, and Eureka Server/Client for service discovery.

Why Externalized Config and Discovery?

Use case: instead of every microservice carrying its own copy of database URLs, feature flags, and secrets, a Config Server hosts them centrally (often backed by a Git repository), and services pull their config at startup. Similarly, instead of hardcoding "order-service is at http://10.0.0.5:8081", a discovery server like Eureka lets services register themselves by name and look each other up dynamically.

Config Server: spring-cloud-config-server

This dependency turns a Spring Boot application into a Config Server — a central place that serves configuration files (typically backed by a Git repository) to every other service in the system.

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-config-server</artifactId>
</dependency>

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

server.port=8888
spring.cloud.config.server.git.uri=https://github.com/your-org/config-repo

Config Client: spring-cloud-starter-config

Any other service adds spring-cloud-starter-config to pull its configuration from the Config Server at startup instead of relying only on its local application.properties.

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

Point the client at the Config Server using spring.config.import (the modern approach, replacing the older bootstrap.yml pattern).

spring.application.name=order-service
spring.config.import=optional:configserver:http://localhost:8888

Eureka Server: spring-cloud-starter-netflix-eureka-server

This dependency turns a Spring Boot application into a Eureka Server — a registry that every other service reports its location to, and that services query to find each other.

<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);
    }
}

Eureka Client: spring-cloud-starter-netflix-eureka-client

Any service that should be discoverable adds this dependency and registers itself with the Eureka Server on startup.

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

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

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

Common Mistakes

Best Practices

Frequently Asked Questions

Summary

spring-cloud-config-server/starter-config centralize configuration across services, while the Eureka server/client dependencies let services register themselves and discover each other by name instead of hardcoded addresses.