This repository contains the source code and hands-on examples for the Enterprise Java and Quarkus Substack publication by Markus Eisele.

If you're working in enterprise software with Java, Quarkus, Jakarta EE, and cloud-native platforms, this is your launchpad for modern development.

EJQ on Substack is a curated collection of technical articles, guides, and deep dives focused on helping developers and architects:

• Build fast, cloud-native apps with Quarkus
• Secure microservices with Vault, TOTP, and secrets management
• Integrate LangChain4j and AI services into Java applications
• Design resilient, scalable systems using Kubernetes and Dev Services
• Understand modern patterns like RAG (Retrieval-Augmented Generation), validation layers, and service guardrails

All content is hands-on, enterprise-relevant, and written for people building real systems—not prototypes.

Each folder in this repository matches an article from the Substack and includes:

• ✅ Complete project setups
• 💡 Example code with comments
• ⚙️ Quarkus configurations and Dev Services integration
• 📦 Maven projects you can run locally with Podman, Ollama, PostgreSQL, etc.

Below are the example projects included in this repository, listed alphabetically. Each project folder is linked for easy access:

A Quarkus-based application that:

• Simulates email generation and processing using AI models
• Integrates LangChain4j for advanced AI capabilities
• Manages tasks via a to-do list

Description:
Uses AI to generate and process emails, demonstrating LangChain4j integration and task management in a Quarkus app.

A file processing application with:

• CSV file upload and parsing
• Automatic table creation with inferred column types
• Metadata tracking of uploads
• REST API endpoints for data access

Description:
Enables uploading and parsing of CSV files, storing data in a database with automatic schema inference and metadata management.

A project demonstrating how to handle exceptions and serve error pages.

An AI-focused project demonstrating:

• Text embedding generation
• Vector similarity search
• AI model integration
• Data processing pipelines

Description:
Explains how to generate and use text embeddings in Java, including similarity search and integration with AI models.

A project demonstrating how to integrate Flyway into your Quarkus applications and manage database schema evolutions.

A project demonstrating database backed internationalization in Quarkus.

A practical example showing:

• QR code generation
• Image processing
• REST API endpoints
• File handling

Description:
Generates QR codes dynamically via REST endpoints and handles image file processing in a Quarkus service.

A Langchain4j based chat-bot system using a local model and websocket next extension.

A project demonstrating:

• Building GraphQL APIs using SmallRye GraphQL
• REST API integration
• Native executable support for high performance

Description:
Shows how to build GraphQL APIs in Quarkus, including REST integration and native build support for performance.

A tutorial project showcasing:

• Custom request interceptors
• Logging and auditing with Quarkus filters
• REST API integration

Description:
Teaches how to implement custom interceptors and filters in Quarkus for logging, auditing, and request processing.

A monitoring application featuring:

• Real-time JVM heap memory monitoring
• WebSocket integration
• Dashboard UI
• Data visualization

Description:
Monitors JVM memory usage in real time, pushing updates to a web dashboard using WebSockets for live visualization.

A utility application showing:

• File resource handling
• Stream processing
• Configuration management
• Error handling

Description:
Provides examples for reading and processing file resources in Quarkus, with robust error and configuration management.

A secure Quarkus application featuring:

• JPA-based user authentication
• PostgreSQL database integration
• REST API endpoints
• Hibernate ORM with Panache

Description:
Demonstrates secure authentication and authorization using JPA entities, with a PostgreSQL backend and RESTful APIs.

A REST API for sentiment analysis featuring:

• Integration with LangChain4j and Ollama
• REST endpoints for text sentiment analysis
• Native executable support for optimal performance

Description:
Implements a sentiment analysis API using AI models, with endpoints for analyzing text and support for native compilation.

A Quarkus application demonstrating form validation with:

• Jakarta Validation annotations
• Localized error messages (English and French)
• REST endpoints with form handling
• Qute templates for HTML rendering

Description:
Shows how to implement robust input validation in Quarkus REST endpoints and web forms, including internationalization of error messages.

This repo will grow with the publication. Planned future topics include:

• Streaming secure file downloads from object stores or databases
• Building developer portals with Backstage and Red Hat Developer Hub
• Using PostgreSQL and Quarkus Dev Services for fast local prototyping
• Implementing advanced AI agents with Java and LangChain4j

Watch the repo or subscribe to the Substack to stay updated.

Stay up to date and reach out through my channels:

• 🐦 Twitter/X: @myfear
• 💻 GitHub: myfear
• 🔗 LinkedIn: Markus Eisele
• 📰 Substack: Enterprise Java and Quarkus

⭐️ Star this repo if you find the content useful.
📢 Share with your team if you're working on Java modernization, AI integration, or cloud-native enterprise apps.