Spring Cloud Config & Centralized Configuration Management[Java Spring Boot Mastery Series – Part 19]

In a microservices architecture, managing configurations across multiple services becomes difficult. Spring Cloud Config provides centralized configuration management, ensuring consistency and dynamic updates without redeploying services.

🎯 Why Centralized Configuration?

✅ Central place to manage configuration for all services
✅ Environment-specific settings (dev, qa, prod)
✅ Dynamic refresh of properties
✅ Secure secrets handling

🧰 Components

Component	Role
Config Server	Central service that provides configurations
Config Client	Your microservices that fetch configs from server
Git/Native backend	Source of config (Git repo, filesystem, etc.)

⚙️ Step-by-Step Setup

🛠️ Step 1: Create the Spring Cloud Config Server

🔸 pom.xml

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

🔸 @EnableConfigServer

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

🔸 application.yml

server:
  port: 8888

spring:
  cloud:
    config:
      server:
        git:
          uri: https://github.com/your-org/config-repo
          clone-on-start: true

📂 In the Git repo, add files like:

• application.yml
• service-a.yml
• service-b-dev.yml
• service-c-prod.yml

🛠️ Step 2: Set Up a Config Client (e.g., Service A)

🔸 pom.xml

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

🔸 bootstrap.yml (or application.yml in latest Spring Boot)

spring:
  application:
    name: service-a
  cloud:
    config:
      uri: http://localhost:8888

💡 spring.application.name must match the file in your Git config repo (service-a.yml)

🧪 Test the Setup

Start:

1. Config Server (port 8888)
2. Service A (port 8080)

Visit:

http://localhost:8888/service-a/default

→ You’ll see the properties from your Git repo.

🔄 Dynamic Property Refresh

Use @RefreshScope on a Spring-managed bean:

@RestController
@RefreshScope
public class GreetingController {

    @Value("${greeting.message}")
    private String message;

    @GetMapping("/greet")
    public String greet() {
        return message;
    }
}

🔁 Trigger Refresh (Actuator Required)

Add Actuator Dependency:

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

Enable refresh endpoint in application.yml:

management:
  endpoints:
    web:
      exposure:
        include: refresh

Trigger refresh:

cu rl -X POST http://localhost:8080 /actuator/refresh

🧱 Git Repo Structure Example

config-repo/
├── application.yml
├── service-a.yml
├── service-b-dev.yml
└── service-c-prod.yml

Spring uses {application-name}-{profile}.yml naming convention.

🔐 Securing Config Server

Add credentials to access Git:

spring:
  cloud:
    config:
      server:
        git:
          username: your-username
          password: your-token

Or use environment variables for secrets.

🔧 Native File-Based Config (Alternative to Git)

spring:
  cloud:
    config:
      server:
        native:
          search-locations: file:///path/to/configs

Use --spring.profiles.active=native when running the config server.

🌍 Real-World Use Case

• Use Git repo for versioned config.
• Services like service-a, service-b, and gateway fetch their configs.
• You can change any property and just call the /actuator/refresh endpoint — no need to restart the service.

✅ Summary

Feature	Benefit
Centralized Config	Manage all configs in one place
Environment Support	Easy separation of dev, prod, etc.
Dynamic Refresh	Update properties without restart
Git Integration	Version control for configs

➡️ Next Up: Part 20 – Spring Cloud Gateway for API Routing & Filters