Spring Boot - Eureka Client

In a microservices architecture, services need a way to locate and communicate with each other dynamically. Eureka Client enables a Spring Boot application to register itself with the Eureka Server and discover other registered services without hardcoding IP addresses or URLs.

• Automatic Service Registration with Eureka Server.
• Dynamic Service Discovery for inter-service communication.
• Simplifies scaling and deployment of microservices.

Why use Eureka Client in Spring Boot Applications?

Eureka Client allows a microservice to become discoverable within a distributed system. Once registered, other services can locate and communicate with it through the Eureka Server.

Benefits of Eureka Client:

• Automatic Registration: Registers the service with Eureka Server during startup.
• Service Discovery: Enables communication using service names instead of IP addresses.
• Dynamic Scaling: Supports multiple service instances automatically.
• Fault Tolerance: Removes unavailable instances from the registry.
• Spring Cloud Integration: Works seamlessly with Spring Boot and Spring Cloud components.

Steps to Configuring the Eureka Client

Follow these steps To Configure a Eureka Client.

Step 1: Create a Spring Boot Project

Create a Spring Boot project using Spring Initializr.

Add Dependencies:

• Spring Web
• Eureka Discovery Client
• Spring Boot DevTools

Step 2: Review the Generated pom.xml File

The generated pom.xml file should look similar to the following:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
         https://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.3.0</version>
        <relativePath/>
    </parent>

    <groupId>org.geeksforgeeks</groupId>
    <artifactId>student-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>student-service</name>
    <description>Spring Boot Eureka Client Example</description>

    <properties>
        <java.version>17</java.version>
        <spring-cloud.version>2023.0.2</spring-cloud.version>
    </properties>

    <dependencies>

        <!-- Spring Boot Web -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

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

        <!-- Spring Boot DevTools -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <!-- Testing -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Step 3: Configure Eureka Client Properties

Configure Eureka-related settings in the application.yml file.

• spring.application.name: defines the service name registered in Eureka.
• register-with-eureka: enables service registration.
• fetch-registry: allows fetching registry information.
• defaultZone: specifies the Eureka Server URL.
• prefer-ip-address: registers the service using its IP address.

server:
port: 8081
spring:
application:
name: API-GATEWAY

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

Step 4: Enable Eureka Client Functionality

The main Spring Boot class is used to start the application and enable Eureka Client functionality.

package org.geeksforgeeks.student;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class StudentApplication {

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

Note: In recent Spring Cloud versions, the @EnableEurekaClient annotation is optional because Eureka Client is enabled automatically when the dependency is present.

Step 5: Create a Sample REST Controller

Create a simple REST endpoint to verify that the service is running successfully.

package org.geeksforgeeks.student.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class StudentController {

    @GetMapping("/students")
    public String getStudents() {
        return "Student Service is Running";
    }
}

Step 6: Run the Eureka Client Application

After configuring the Eureka Client, run the Spring Boot application to register it with the Eureka Server.

• Right-click StudentApplication.java
• Then select -> Run 'StudentApplication'

Alternatively, you can run the application using Maven:

mvn spring-boot:run

Open the Eureka Dashboard:

http://localhost:8761

When the application starts successfully, it automatically registers itself with the Eureka Server and you should see the registered service:

• API-GATEWAY
• STUDENT-APP
• TEACHER-APP

Step 7: Access the Client Service

Open your browser and hit the Url to Access the service:

http://localhost:8081/students

Output:

Student Service is Running

Use Cases

Eureka Client is commonly used in:

• Microservices-based applications.
• Service discovery environments.
• Cloud-native applications.
• Auto-scaling systems.
• Load-balanced architectures.