README.md

🚀 J2EE Transaction Backend Template

A robust and modular J2EE backend template for handling transaction-based applications. Perfect for kickstarting your transaction microservices, financial applications, or any Java EE-based backend.

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📑 Table of Contents

1. ⚙️ Project Overview

2. 🛠️ Technologies & Dependencies

3. 📂 Project Structure & Hierarchy

4. 🚀 Getting Started

   • Prerequisites
   • Clone & Build
   • Deploy & Run

5. 📝 Configuration & Usage

6. ✨ Key Modules & Packages

7. 🛡️ Security & Transaction Management

8. ⭐ Contribution & Guidelines

9. 📜 License

10. 📬 Contact & Support

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⚙️ Project Overview

This J2EE Transaction Backend Template provides a ready-to-use skeleton for developing enterprise-grade transaction processing services. It follows best practices in Java EE architecture and modular design, letting you focus on business logic rather than boilerplate code.

• Modular Architecture: Separates concerns into controller, service, repository, and model layers.
• Transaction Management: Leverages JTA (Java Transaction API) or container-managed transactions to ensure ACID compliance.
• Configuration-Driven: Uses an external application.properties (or xml) for easy environment-specific setups.
• Extensible & Maintainable: Designed to add or replace modules (e.g., integrate with different databases, add security filters) without major refactor.

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🛠️ Technologies & Dependencies

Below are the main technologies and frameworks used in this template. Adjust versions in the pom.xml as needed.

• Java EE / Jakarta EE (Servlets, JSP, JPA)
• Maven 🎯 for build and dependency management
• JPA/Hibernate 🗃️ for ORM and entity mapping
• Tomcat / WildFly / GlassFish (as a Servlet container / application server)
• H2 / MySQL / PostgreSQL (switchable via JDBC driver)
• JUnit / Mockito for unit and integration testing
• SLF4J / Logback for logging
• JSON-B / Jackson for JSON serialization
• Docker (optional) for containerized deployments

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📂 Project Structure & Hierarchy

A clear, standardized layout makes navigation and maintenance a breeze. Below is the full folder hierarchy and explanations.

J2EE-Transaction-Bankend-Template/      🔧 Top-level project root  
├── .idea/                              📝 IDE configuration (IntelliJ IDEA)  
├── src/                                💻 Source code directory  
│   ├── main/                           🔨 Main application code  
│   │   ├── java/                       📜 Java source files  
│   │   │   └── com/                    🌐 Base package (replace with your domain)  
│   │   │       └── transaction/        🏷️ Application-specific package  
│   │   │           ├── controller/     🗂️ REST / Servlet controllers  
│   │   │           ├── service/        ⚙️ Business logic & transaction services  
│   │   │           ├── repository/     🗃️ DAO layer for database access  
│   │   │           ├── model/          📦 Entity classes and DTOs  
│   │   │           ├── util/           🔧 Utility helpers (e.g., validators)  
│   │   │           └── config/         📐 Configuration classes (e.g., DataSource, JPA)  
│   │   └── resources/                  🔑 Non-Java resources  
│   │       ├── META-INF/               🗂️ Persistence configuration (`persistence.xml`)  
│   │       ├── application.properties   ⚙️ Environment variables (DB URL, credentials)  
│   │       ├── logback.xml             📝 Logging configuration  
│   │       └── static/                  🎨 Static resources (if any)  
│   └── test/                           🧪 Test sources (unit & integration)  
│       └── java/                       📜 Test Java files mirroring package structure  
│           └── com/                    🌐 Base package for tests  
│               └── transaction/        🏷️ Test cases for modules  
├── target/                            📦 Compiled artifacts (auto-generated)  
│   ├── *.war / *.jar                   🎯 Build outputs  
│   └── ...                             📑 Other build-specific directories  
├── .gitignore                         🚫 Files and folders ignored by Git  
├── .gitattributes                     🎚️ Git attributes configuration  
├── pom.xml                            🛠️ Maven project descriptor (dependencies, plugins)  
└── README.md                          📖 This documentation file  

Note: Package names (com.transaction.*) should be adapted to your organization’s domain (e.g., com.yourcompany.transaction).

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🚀 Getting Started

Follow these steps to get a local copy up and running.

📋 Prerequisites

• Java Development Kit (JDK) 11 or higher
• Maven 3.6+
• A Java EE Compliant Application Server (e.g., Tomcat 9+, WildFly 21+, or GlassFish 5+)
• Git (for cloning)
• Database (MySQL, PostgreSQL, or H2 for in-memory testing)

📥 Clone & Build

1. Clone the repository:

   git clone https://github.com/Tharindu714/J2EE-Transaction-Bankend-Template.git
   cd J2EE-Transaction-Bankend-Template

2. Build with Maven:

   mvn clean package

   • This will compile source code, run tests, and package the application into a WAR (or JAR if configured).
   • The final artifact will be located under target/ (e.g., target/transaction-backend.war).

🚢 Deploy & Run

1. Configure database (in src/main/resources/application.properties or persistence.xml):

   # Example for MySQL
   db.driver=com.mysql.cj.jdbc.Driver  
   db.url=jdbc:mysql://localhost:3306/transactiondb  
   db.username=root  
   db.password=YourPassword  

2. Deploy to your application server:

   • Copy the generated WAR (target/transaction-backend.war) to <TOMCAT_HOME>/webapps/ (or equivalent for WildFly/GlassFish).
   • Start (or restart) the server.
   • Access the application at http://localhost:8080/transaction-backend/ (adjust context path as needed).

Tip: For in-memory testing, switch to H2 by updating application.properties:

db.driver=org.h2.Driver  
db.url=jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE  
db.username=sa  
db.password=  

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📝 Configuration & Usage

Detailed explanation of key configuration files and how to customize them.

1. pom.xml

• Defines project coordinates (groupId, artifactId, version).
• Dependencies: J2EE APIs, JDBC drivers, JPA/Hibernate, logging, testing frameworks.
• Plugins: Maven Compiler Plugin, Maven War Plugin, Surefire (for tests), etc.

🔧 Tip: Adjust dependency versions to match your corporate standards or to mitigate security vulnerabilities (e.g., upgrade Hibernate or Jackson).

2. application.properties (or persistence.xml)

• Database Config: Driver, URL, credentials, dialect (for Hibernate).
• JPA Settings: Show SQL, DDL auto (e.g., hibernate.hbm2ddl.auto=update).
• Logging: Adjust log levels (INFO, DEBUG) for troubleshooting.

3. logback.xml

• Logging Layout: Customize log patterns, appenders (Console, File).
• Log Levels: Set root or package-specific log levels.

4. web.xml (if using traditional Servlets)

• Servlet Mapping: Define servlet classes and URL patterns (e.g., /api/*).
• Filters: Add security filters, CORS filters, or request logging filters.
• Listener: Context listeners (e.g., ContextLoaderListener for Spring integration).

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✨ Key Modules & Packages

Below is a high-level description of the main Java packages and their responsibilities.

1. controller/

• Purpose: Exposes endpoints (RESTful or JSP/Servlet-based).

• Examples:

  • TransactionController.java ➡️ Handles incoming HTTP requests for creating, updating, and querying transactions.
  • UserController.java ➡️ Manages user-related operations (login, registration).

2. service/

• Purpose: Implements business logic and orchestrates transactions.

• Transaction Management: Annotated with @Transactional (JTA-managed in container) to ensure atomic operations.

• Examples:

  • TransactionService.java ➡️ Validates transaction data, calls repository layer, handles exceptions.
  • UserService.java ➡️ Encrypts passwords, manages user roles/permissions.

3. repository/

• Purpose: Data Access Object (DAO) layer—communicates with the database.

• JPA Repositories: Uses EntityManager or Spring Data JPA interfaces for CRUD operations.

• Examples:

  • TransactionRepository.java ➡️ CRUD methods for Transaction entities.
  • UserRepository.java ➡️ Queries for User entities (e.g., find by email).

4. model/

• Purpose: Entity classes (mapped to DB tables) and DTOs (Data Transfer Objects).

• Examples:

  • Transaction.java ➡️ JPA entity with fields like id, amount, timestamp, status.
  • User.java ➡️ JPA entity for user credentials and profile data.
  • ErrorResponse.java ➡️ Standard DTO for API error messages (code, message).

5. util/

• Purpose: Common utilities & helpers used across modules.

• Examples:

  • ValidationUtil.java ➡️ Bean validation helpers, custom annotations.
  • DateUtil.java ➡️ Formatters for date/time operations.

6. config/

• Purpose: Centralized application configuration.

• Examples:

  • DataSourceConfig.java ➡️ Defines DataSource bean, connection pooling (HikariCP).
  • JPAConfig.java ➡️ Sets up EntityManagerFactory, transaction manager.

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🛡️ Security & Transaction Management

🔐 Security

• Authentication & Authorization: Typical setups include JWT, session-based auth, or container-managed security realms.
• Filter Chain: Implement a SecurityFilter to intercept requests, validate JWT tokens, and check user roles/permissions.
• Password Encryption: Use BCrypt or PBKDF2 for hashing user passwords.

📝 Note: Out-of-the-box, this template assumes no strict security; it is up to you to integrate your preferred security framework (e.g., Apache Shiro, Spring Security, or Java EE Security API).

🔄 Transaction Management

• Container-Managed Transactions: Annotate service methods with @Transactional (JTA) so the application server handles commit/rollback automatically.
• Programmatic Transactions: For advanced scenarios, use UserTransaction to demarcate transactions manually.
• Isolation & Propagation: Leverage default READ_COMMITTED isolation; adjust as per use-case (e.g., SERIALIZABLE for high data integrity).

🚀 Pro Tip: To ensure ACID compliance in high-load scenarios, consider two-phase commit (2PC) when integrating multiple resources (e.g., JMS + RDBMS).

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⭐ Contribution & Guidelines

We welcome contributions to improve this template!

1. Fork the repository.

2. Create a feature branch:

   git checkout -b feature/awesome-feature

3. Commit your changes:

   git commit -m "Add awesome-feature"

4. Push to your fork:

   git push origin feature/awesome-feature

5. Open a Pull Request (PR) against the main branch of this repo.

Guidelines:

• Write clean, self-documenting code and follow Java Code Conventions.
• Add unit/integration tests for new features (JUnit 5, Mockito).
• Update this README.md if you modify project structure or add new modules.
• Use meaningful commit messages (e.g., feat:, fix:, docs:, refactor:).

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📜 License

This project is licensed under the MIT License. See the LICENSE file for details.

MIT License

Copyright (c) 2025 Your Name

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction...

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📬 Contact & Support

• Repository Owner: Tharindu714 (@Tharindu714)
• Issues & Bugs: Please file an issue on GitHub under Issues.
• Email: your.email@example.com

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Made with ❤️ and ☕ by the J2EE Community

End of README.md