Kotlin Microservice with Spring Boot

Detailed description can be found here: Kotlin Microservice with Spring Boot

A demonstration microservice built with Spring Boot and Kotlin showcasing modern microservice patterns, cloud-native development, and DevOps practices.

🚀 Features

• RESTful API for Person entity management (CRUD operations)
• In-memory data store with 1000 auto-generated fake records using DataFaker
• Spring Boot Actuator integration with health checks and metrics
• Prometheus metrics exposure for monitoring
• OpenAPI/Swagger documentation
• Multiple web server support (Tomcat, Jetty, Undertow)
• Cloud-native deployment configurations (Kubernetes, OpenShift)
• Containerization with Jib Maven plugin
• CI/CD pipeline with Azure DevOps
• Development tools integration (Skaffold, DevFile)

🛠 Technology Stack

Technology	Version	Purpose
Spring Boot	3.5.0	Application framework
Kotlin	2.1.21	Programming language
Java	17	Runtime platform
Maven	3.6+	Build tool
SpringDoc OpenAPI	2.8.8	API documentation
Micrometer	1.11.4	Metrics collection
DataFaker	2.4.3	Test data generation
Instancio	5.4.1	Test object creation

🏃‍♂️ Quick Start

Prerequisites

• Java 17 or higher
• Maven 3.6+
• (Optional) Docker for containerization
• (Optional) Kubernetes/OpenShift for deployment

Running the Application

1. Clone the repository

git clone https://github.com/piomin/sample-spring-kotlin-microservice.git
cd sample-spring-kotlin-microservice

2. Run with Maven

mvn spring-boot:run

3. Access the application

• Application: http://localhost:8080
• Swagger UI: http://localhost:8080/swagger-ui.html
• Health Check: http://localhost:8080/actuator/health
• Metrics: http://localhost:8080/actuator/prometheus

📋 API Documentation

Person Management Endpoints

Method	Endpoint	Description	Response
GET	/persons	Retrieve all persons	List
GET	/persons/{id}	Get person by ID	Person
GET	/persons/ages/{age}	Find persons by age	List
GET	/persons/delayed	Get all persons with random delay	List
POST	/persons	Create new person	Person
PUT	/persons	Update existing person	Person
DELETE	/persons/{id}	Delete person by ID	Boolean

Environment Endpoint

Method	Endpoint	Description
GET	/envs	Get environment password variable

🔧 Build & Package

Maven Commands

# Compile and run tests
mvn clean compile test

# Package application
mvn clean package

# Skip tests during build
mvn clean package -DskipTests

# Run with a specific profile (jetty, undertow)
mvn spring-boot:run -Pjetty

Docker Build

# Build with Jib (preferred)
mvn clean compile jib:dockerBuild -Pjib

# Build with Dockerfile
docker build -t sample-spring-kotlin-microservice .

☸️ Deployment

Kubernetes

kubectl apply -f k8s/
kubectl get pods -l app=sample-spring-kotlin-microservice
kubectl port-forward svc/sample-spring-kotlin-microservice 8080:8080

OpenShift

oc process -f openshift/app.yaml \
  -p namespace=my-project \
  -p version=latest | oc apply -f -

🧪 Testing

# Run all tests
mvn test

# Run a specific test class
mvn test -Dtest=PersonControllerTests

# Generate coverage report
mvn clean test jacoco:report

📊 Monitoring & Observability

curl http://localhost:8080/actuator/health
curl http://localhost:8080/actuator/metrics
curl http://localhost:8080/actuator/prometheus

⚙️ Configuration

application.yml highlights

spring:
  application.name: sample-spring-kotlin-microservice
management:
  endpoints.web.exposure.include: '*'
  endpoint.health:
    show-details: always
    probes.enabled: true
app:
  delay: 20

🔨 Development Setup

IntelliJ IDEA

1. Import as Maven project
2. Install Kotlin plugin
3. Set Project SDK to Java 17
4. Enable annotation processing

VS Code

• Install Extension Pack for Java
• Kotlin Language Support
• Spring Boot Extension Pack

🚦 CI/CD Pipeline

• Azure DevOps pipeline for build, test, and container image creation
• SonarCloud integration for quality gate
• Automatic triggers on master and PR validation

📁 Project Structure

sample-spring-kotlin-microservice/
├── src/
│   ├── main/kotlin/pl/piomin/services/
│   ├── main/resources/application.yml
│   └── test/kotlin/pl/piomin/services/
├── k8s/
├── openshift/
├── azure-pipelines.yml
├── skaffold.yaml
├── devfile.yaml
├── Dockerfile
└── pom.xml

🤝 Contributing

1. Fork the repo
2. Create a feature branch (git checkout -b feature/awesome)
3. Commit changes (git commit -m 'feat: awesome feature')
4. Push and open a PR

📝 License

This project is provided as a sample/demo for educational purposes.

📞 Support

For questions, open an issue or refer to:

• Spring Boot Docs: https://spring.io/projects/spring-boot
• Kotlin Docs: https://kotlinlang.org/docs/