Legacy Modernization Reference Application (LMRA)

🌐 Language: English | Português

A comprehensive reference application demonstrating how to modernize legacy codebases using modern technologies, cloud-native architectures, and best practices.

🎯 Project Goals

This project showcases:

• Legacy Code Modernization: Upgrading deprecated frameworks and technologies
• Multi-Language Microservices: Java (Spring Boot), C# (.NET), and Node.js working together
• Cloud-Native Architecture: Containerized services with Docker and AWS
• Full-Stack Application: Web frontend (Next.js), Android mobile app (Kotlin + Compose)
• Modern DevOps Practices: CI/CD, Infrastructure as Code, Observability
• AI Integration: Self-hosted LLM (Ollama) for intelligent features

📁 Project Structure

challenge_2025/
├── services/
│   ├── users-java/          # Users service (Spring Boot 3 + JDK 21)
│   ├── tickets-dotnet/      # Tickets service (.NET 8 minimal APIs)
│   └── ai-gateway-node/     # AI Gateway (Node.js + Ollama)
├── web/
│   └── nextjs/              # Web frontend (Next.js + TypeScript)
├── mobile/
│   └── android-compose/     # Android app (Kotlin + Jetpack Compose)
├── infra/
│   └── terraform/           # Infrastructure as Code (Terraform)
├── ops/
│   ├── docker/              # Dockerfiles and compose files
│   └── ci-cd/               # CI/CD pipelines (GitHub Actions)
├── docs/
│   ├── migration-playbook.md
│   └── decisions/           # Architecture Decision Records
└── legacy/                  # Legacy code examples for reference

🏗️ Architecture

Services

1. Users Service (Java)

   • Technology: Spring Boot 3.x, JDK 21
   • Responsibilities: User authentication, profile management
   • Database: PostgreSQL (shared)
   • Port: 8080

2. Tickets Service (C#)

   • Technology: .NET 8 minimal APIs
   • Responsibilities: Ticket/ticket management, workflow
   • Database: PostgreSQL (shared)
   • Port: 8081

3. AI Gateway Service (Node.js)

   • Technology: Node.js + Express
   • Responsibilities: Proxy to Ollama, AI-powered features
   • Models: LLM for summaries, embeddings for search
   • Port: 8082

Frontends

1. Web Application (Next.js)

   • Technology: Next.js 14, React 18, TypeScript
   • Responsibilities: Primary user interface
   • Authentication: AWS Cognito
   • Port: 3000
   • Internationalization: Full support for English and Portuguese with next-intl
   • UI Features: Modern dark theme with black background, animated DNA helix visualization, rolling slider with Chinese phrase, Arimo font family, language switcher

2. Android Application

   • Technology: Kotlin 2.x, Jetpack Compose
   • Responsibilities: Mobile access to all features
   • Authentication: AWS Cognito

🚀 Getting Started

Prerequisites

• Docker & Docker Compose
• JDK 21 (for local Java development)
• .NET 8 SDK (for local C# development)
• Node.js 20+ (for local frontend development)
• PostgreSQL 16 (or use Docker)
• Android Studio (for Android development)
• Terraform (for infrastructure provisioning)

Quick Start (Docker)

# Start all services
docker-compose up -d

# View logs
docker-compose logs -f

# Stop all services
docker-compose down

Local Development

Each service has its own README with specific setup instructions. See individual directories:

• services/users-java/README.md
• services/tickets-dotnet/README.md
• web/nextjs/README.md
• mobile/android-compose/README.md

🔄 Migration Storyline

This project demonstrates modernization of:

• Java EE → Spring Boot 3: XML configuration to Java config, Jakarta EE migration
• .NET Framework → .NET 8: Web API to minimal APIs, nullable reference types
• jQuery → Next.js: Server-side rendering and modern React patterns
• XML Layouts → Jetpack Compose: Declarative UI on Android

See docs/migration-playbook.md for detailed guides.

🛠️ Technology Stack

Backend

• Java: Spring Boot 3.x, JDK 21, Spring Security 6
• C#: .NET 8, Minimal APIs, Entity Framework Core 8
• Node.js: Node 20+, Express, TypeScript

Frontend

• Web: Next.js 14, React 18, TypeScript, Tailwind CSS, Arimo font
• Mobile: Kotlin 2.x, Jetpack Compose, Ktor, Room

Database

• PostgreSQL 16
• Migrations: Flyway (Java) + EF Core Migrations (C#)

Infrastructure

• Containerization: Docker, Docker Compose
• Cloud: AWS (ECS Fargate, RDS, S3, CloudFront, Cognito)
• IaC: Terraform
• CI/CD: GitHub Actions
• Monitoring: OpenTelemetry, Grafana/CloudWatch

AI

• Self-hosted: Ollama
• Models: Llama 3, Qwen2
• Use cases: Ticket summaries, code modernization suggestions

🎨 UI/UX Features

The web application features a modern, minimalist design:

• Internationalization (i18n): Full support for English and Portuguese languages
  • Language switcher in top-right corner on all pages
  • Locale-aware routing (/en/* and /pt/*)
  • All user-facing text translated
  • Automatic locale detection and persistence
• Dark Theme: Full black background with a subtle white grid pattern for depth
• Animated DNA Visualization: Interactive 3D canvas-based DNA helix animation with continuous rotation
• Rolling Slider: Infinite-scrolling banner with the Chinese phrase "现代化旧代码库的完整参考指南" (A comprehensive reference guide for modernizing legacy codebases)
• Typography: Arimo font family for a clean, modern look across all pages
• Card-Based Layout: Black cards with white borders and hover effects
• Global Components: Consistent footer ("All rights reserved to SNK") and rolling slider on all pages
• Responsive Design: Optimized for all screen sizes with Tailwind CSS

📚 Documentation

• Migration Playbook
• Architecture Decision Records
• API Documentation
• Deployment Guide

🤝 Contributing

See CONTRIBUTING.md for guidelines.

📝 License

MIT License - see LICENSE file for details.

🎓 Learning Outcomes

After working through this project, you'll understand:

• How to modernize legacy codebases incrementally
• Building and operating microservices with multiple languages
• Cloud-native deployment patterns
• Modern frontend and mobile development
• Infrastructure as Code and CI/CD best practices
• Integration of AI capabilities into applications

🌐 Language

• English
• Português