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Explanation

After creating the Eureka Server, each Spring Boot microservice can register itself as a Eureka Client. This allows Eureka to maintain a registry of available services.

Code:

                 Eureka Server
                    :8761
                       ▲
              register│
        ┌──────────────┼──────────────┐
        │              │              │
   User Service   Order Service   Payment Service
      :8081          :8082           :8083

Explanation

Add the Eureka Client dependency to the Spring Boot microservice. Spring Cloud Netflix Eureka Client provides the functionality required to register the service with Eureka.

Code:

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

Explanation

Configure the microservice name and Eureka Server URL in application.properties. The service name is important because other microservices can use it to discover this service.

Code:

spring.application.name=user-service
server.port=8081

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

Explanation

The Eureka Client automatically registers the Spring Boot application with Eureka when the application starts. In modern Spring Cloud versions, explicit @EnableEurekaClient is generally not required when the Eureka Client dependency is present.

Code:

@SpringBootApplication
public class UserServiceApplication {

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

Explanation

Start the Eureka Server first and then start the microservices. Each service registers its application name, host, port, and availability information with Eureka.

Code:

Start Eureka Server
        ↓
http://localhost:8761
        ↓
Start User Service
        ↓
Start Order Service
        ↓
Eureka Registry
        ├── USER-SERVICE :8081
        └── ORDER-SERVICE :8082

Explanation

Once the services are registered, open the Eureka dashboard to verify them. The registered services appear under the Instances currently registered with Eureka section.

Code:

Eureka Dashboard

Instances currently registered:

USER-SERVICE     UP (1)
ORDER-SERVICE    UP (1)

UP = Service is available