JPA Multi-Database Testing Project

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This project explores how to configure and interact with multiple databases using JPA. It includes PostgreSQL and MySQL setups with a flexible DAO structure and test coverage across three persistence units.

📁 Project Overview

The project began with support for two PostgreSQL databases and later extended to include a third MySQL database. It demonstrates how to:

• Structure JPA DAOs to support multiple persistence units;
• Perform CRUD operations across PostgreSQL and MySQL simultaneously;
• Use environment variables for database credentials;
• Write unit tests for each database configuration.

🧪 Technologies Used

• Java 21
• JPA
• JUnit 5
• PostgreSQL
• MySQL
• Spring Tools Suite 4 (STS4)

⚙️ Setup Instructions

1. Make sure you have Java 17+ installed (Project tested on Java 21);
2. Install both PostgreSQL and MySQL databases locally or configure remote instances;
3. Create and configure the following environment variables:
   • DB_URL – JDBC URL for your default database (used by DB1);
   • DB_USERNAME – Your DB username;
   • DB_PASSWORD – Your DB password.
4. Edit persistence.xml in the META-INF folder if necessary to adjust connection URLs and driver properties;
5. Run the test classes to validate integration across databases.

📜 Commit Highlights

• Project Setup – Initialized the project based on a previous JDBC migration structure;
• Two DB Support – Added DAOs and tests for PostgreSQL using two persistence units;
• Three DB Support – Integrated MySQL as a third database with new DAO and test class;
• Full Documentation – Added Javadocs to all entity, DAO, and test classes with internal links for easy navigation.

📝 Notes

• Make sure to include the required JAR files for MySQL/PostgreSQL in your classpath;
• All required JAR files are located in the project-files folder;