Spring Boot with Kotlin and JPA Example

A modern Spring Boot microservice demonstrating cloud-native application development with Kotlin, JPA, and comprehensive multi-platform deployment strategies.

What's Inside

Spring Boot 3.5.6 with Java 21 - Latest LTS foundation
Kotlin 2.2.20 - Modern, expressive language
Multi-module architecture - Domain and web separation
Cloud Native Buildpacks - Container images without Dockerfiles
Dual build support - Both Maven and Gradle
Multi-platform deployments - AWS, Azure, Google Cloud, Tanzu Platform
Production-ready - Actuator, metrics, health checks

Quick Start

Prerequisites

Java 21 (LTS) - Required for Spring Boot 3.5.6
Docker - For database and container builds
Git - For version control

Optional but recommended:

HTTPie - API testing
jq - JSON processing

Get Started in 3 Steps

# 1. Clone and build
git clone https://github.com/pacphi/spring-boot-with-kotlin-and-jpa-example.git
cd spring-boot-with-kotlin-and-jpa-example
./mvnw package  # or ./gradlew build

# 2. Start database
docker run -d -p 5432:5432 -e POSTGRES_PASSWORD=postgres -e POSTGRES_DB=geo_data postgres:15

# 3. Run application
./mvnw -pl cities-web spring-boot:run -Dspring.profiles.active=postgres,seeded

Verify it works:

curl http://localhost:8080/cities | jq .

Architecture

This application demonstrates domain-driven design with clear separation:

cities-domain - Business logic, entities, and repositories
cities-web - REST API, controllers, and web configuration

Key Features:

RESTful API with HATEOAS support
PostgreSQL with Flyway migrations
Comprehensive monitoring with Actuator
Multi-environment configuration profiles
Container-first deployment approach

→ See full architecture details

Build and Run

Choose your build tool:

Maven - Traditional XML-based configuration
Gradle - Modern, flexible build system

Quick build commands:

# Maven
./mvnw package

# Gradle
./gradlew build

→ See complete build guide

Deployment Options

This application showcases deployment strategies across major cloud platforms:

🚀 Quick Deploy

Local Development - Docker Compose, embedded database options
Docker - Cloud Native Buildpacks (no Dockerfile needed!)

🏗️ Kubernetes & Orchestration

Minikube - Local Kubernetes development with 2025 features (AI workloads, enhanced security)
KOPS - Production Kubernetes on AWS with full infrastructure management
Juju - Model-driven operations and multi-cloud application management

☁️ Cloud Platforms (2025 Ready)

AWS EKS - Latest Kubernetes 1.33+, EKS Automatic, advanced security
Azure AKS - AKS Automatic, Azure Linux migration, AI/ML integration
Google Cloud GKE - AI-powered features, TPU support, latest performance improvements
Tanzu Platform - Cloud Foundry v10.0, simplified developer experience

📋 Complete Guides

Each deployment guide includes:

2025 platform updates and new features
Step-by-step instructions with code examples
Security best practices and compliance
CI/CD pipeline examples (GitHub Actions, Jenkins, etc.)
Cost optimization strategies
Monitoring and troubleshooting guides

API Documentation

Endpoints

Method	Path	Description
`GET`	`/cities`	List all cities
`GET`	`/cities/{id}`	Get city by ID
`POST`	`/cities`	Create new city
`PUT`	`/cities/{id}`	Update existing city
`DELETE`	`/cities/{id}`	Delete city

Example Usage

# List cities
curl http://localhost:8080/cities | jq .

# Create city
curl -X POST http://localhost:8080/cities \
  -H "Content-Type: application/json" \
  -d '{
    "id": "NYC",
    "name": "New York City",
    "description": "The Big Apple",
    "location": {"latitude": 40.7128, "longitude": -74.0060}
  }'

# Update city
curl -X PUT http://localhost:8080/cities/NYC \
  -H "Content-Type: application/json" \
  -d '{"description": "Updated description"}'

Monitoring Endpoints

Spring Boot Actuator provides production-ready monitoring:

/actuator/health - Application health status
/actuator/metrics - Application metrics
/actuator/prometheus - Prometheus-format metrics
/actuator/info - Application information

→ See complete API documentation

Development Guide

Project Structure

├── cities-domain/          # Business logic and entities
│   ├── src/main/kotlin/   # Domain services and repositories
│   └── src/test/kotlin/   # Domain tests
├── cities-web/            # REST API and web layer
│   ├── src/main/kotlin/   # Controllers and configuration
│   └── src/test/kotlin/   # Integration tests
├── docs/                  # Documentation
└── specs/                 # Deployment configurations
    ├── docker/           # Docker Compose files
    └── k8s/              # Kubernetes manifests

Technologies Used

Backend: Spring Boot 3.5.6, Kotlin 2.2.20, Java 21
Database: PostgreSQL 15+ with Flyway migrations
Containerization: Cloud Native Buildpacks, Docker
Monitoring: Spring Actuator, Micrometer, Prometheus
Testing: JUnit 5, MockK, TestContainers

→ See detailed architecture

Documentation

📚 Comprehensive Guides

Core Documentation

Architecture - Application design, patterns, and structure
Build - Maven/Gradle builds, CI/CD, container creation
Run - Local development, configuration, API testing

Cloud Deployments

AWS Deployment - EKS, ECR, RDS, latest 2025 features
Azure Deployment - AKS, ACR, PostgreSQL, AKS Automatic
Google Cloud Deployment - GKE, Artifact Registry, Cloud SQL, AI features
Tanzu Platform Deployment - Cloud Foundry v10.0, service bindings

Kubernetes & Orchestration

Minikube - Local Kubernetes development, AI workload support, security hardening
KOPS - Production-grade Kubernetes on AWS, auto-scaling, monitoring
Juju - Model-driven operations, charms, multi-cloud management

Reference

Appendices - Tools, commands, troubleshooting, reference

🛠 Quick References

Tool Installation - All required tools and CLIs
Command Reference - Maven, Gradle, Docker, kubectl commands
Configuration Templates - Ready-to-use config files
Troubleshooting - Common issues and solutions

Contributing

Fork the repository
Create a feature branch (git checkout -b feature/amazing-feature)
Commit your changes (git commit -m 'Add amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

What's New in 2025

This project demonstrates the latest cloud-native development practices:

✅ Java 21 LTS - Latest long-term support release
✅ Spring Boot 3.5.6 - Modern Spring ecosystem
✅ Cloud Native Buildpacks - Dockerfile-free containerization
✅ Multi-platform deployment - AWS, Azure, Google Cloud, Tanzu Platform
✅ Advanced Kubernetes - Latest features across all major cloud providers
✅ AI/ML Ready - Supports latest cloud AI/ML integrations
✅ Security Best Practices - Pod Security Standards, RBAC, Zero Trust

License

This project is licensed under the Apache 2.0 License - see the LICENSE file for details.

Acknowledgments

Built upon ideas from the codecentric blog article
Demonstrates cloud-native patterns and multi-platform deployment strategies
Updated for 2025 with latest platform features and best practices