☕ Context & Dependency Injection with Java EE (Jakarta EE)

This project demonstrates the power of Jakarta Contexts and Dependency Injection (CDI) by implementing a modular and extensible notification system using qualifiers, scopes, and event-based logging.

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📚 Project Overview

The goal of this project is to show how Java EE (Jakarta EE) technologies can be used to create loosely-coupled, pluggable components. Using CDI, it supports injecting different implementations of services like email and SMS notifications based on custom annotations (@Email, @SMS, @Console), and observes events to provide centralized logging.

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🧠 Key Concepts Demonstrated

Concept	Description
CDI (Jakarta EE)	Enables dependency injection and event-based communication between loosely coupled components.
Custom Qualifiers	@Email, @SMS, @Console used to differentiate between multiple implementations of an interface.
Dependency Injection	Beans like EmailNotifier and SMSNotifier are injected wherever required.
ApplicationScoped Beans	Managed bean lifecycle across the application.
Event Observers	Centralized logging by observing fired events.

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🧱 Project Structure

Context & Dependency Injection/
├── CDIModule/
│   ├── src/
│   │   ├── main/java/com/deltacodex/ee/
│   │   │   ├── annotation/              # Contains custom qualifier annotations
│   │   │   │   ├── Console.java
│   │   │   │   ├── Email.java
│   │   │   │   └── SMS.java
│   │   │   ├── CDI/                     # CDI beans and services
│   │   │   │   ├── EmailNotifier.java
│   │   │   │   ├── SMSNotifier.java
│   │   │   │   ├── NotificationService.java
│   │   │   │   ├── Service.java
│   │   │   │   └── Logger.java
│   │   │   └── ejb/                     # EJB session beans (e.g., UserRegistration)
│   │   │       └── UserRegistrationSessionBean.java
│   └── pom.xml                          # Maven configuration for building the module

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🔍 Key Files Explained

1. @Email, @SMS, @Console

• These are custom CDI qualifiers to distinguish between different injectable implementations.
• Example use: @Inject @Email NotificationService service;

2. EmailNotifier.java

@Email
@ApplicationScoped
public class EmailNotifier implements NotificationService {
    public void sendNotification(String message) {
        System.out.println("Email Notifier Sending Email... " + message);
    }
}

• Injected where @Email is specified.
• Prints a mock email-sending log to the console.

3. Logger.java

@ApplicationScoped
public class Logger {
    public void log(@Observes String message) {
        System.out.println("Logged :" + message);
    }

    public void logText(@Observes @Console String message) {
        System.out.println("Text Logged :" + message);
    }
}

• This bean listens for fired string events and logs them.
• Demonstrates event-based communication in CDI.

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🏗️ How to Build and Run

✅ Prerequisites

• Java 11+
• Maven
• GlassFish 5 or 6 (for Jakarta EE support)

🔧 Build

cd "Context & Dependency Injection/CDIModule"
mvn clean install

🚀 Deploy

1. Deploy the .war or .ear (depending on your configuration) to a Jakarta EE compatible server like GlassFish.
2. Use the Admin Console or asadmin CLI tool for deployment.

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🤖 How It Works (Example Flow)

1. You inject NotificationService with a qualifier like @Email or @SMS.

2. When sendNotification("Hello!") is called:

   • EmailNotifier prints: "Email Notifier Sending Email... Hello!"

3. If a String event is fired:

   • Logger automatically logs: "Logged :Hello!"
   • If qualified with @Console, logText() is used.

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💡 Use Case Ideas

• User registration systems sending confirmation via Email/SMS
• Plugin-based notification architecture
• Event-driven auditing/logging system

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📜 License

This project is intended for educational and demonstration purposes only. No commercial license included.

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👨‍💻 Author

DeltaCodex – Java EE Demonstration Repository Feel free to fork, star ⭐, or contribute!