🚀 Java EJB RMI - Core, AppModule & WebApp (Currency Converter App)

Overview

This repository contains three modular Java projects demonstrating the use of Enterprise JavaBeans (EJB), Remote Method Invocation (RMI), and Web Integration with JSP. The projects work together to create a simple application for currency conversion, featuring a modular design with a Core module, an AppModule (EJB implementation), and a WebApp (Servlet-based web interface).

📽️ Demo Video

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Table of Contents

1. Project Structure
2. Core Module
3. AppModule (EJB)
4. WebApp
5. Running the Application
6. Technologies Used
7. License

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📁 Project Structure

Java-EJB-RMI/
├── Core/
│   ├── src/main/java/lk/jiat/web/core/remote/CurrencyConverter.java
│   └── pom.xml
│
├── AppModule/
│   ├── src/main/java/lk/jiat/web/ejb/CurrencyConverterBean.java
│   └── pom.xml
│
└── WebApp/
    ├── src/main/java/lk/jiat/web/servlet/Home.java
    ├── src/main/webapp/index.jsp
    └── pom.xml

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🔑 Core Module

The Core module defines the CurrencyConverter interface used for the conversion between USD and LKR. This is a remote interface, implemented by the AppModule.

Key Files:

• CurrencyConverter.java: Defines the remote interface for currency conversion.

Code:

package lk.jiat.web.core.remote;

import jakarta.ejb.Remote;

@Remote
public interface CurrencyConverter {
    double convertToLKR(double amount);
    double convertToUSD(double amount);
}

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⚙️ AppModule (EJB)

The AppModule implements the CurrencyConverter interface and contains the actual business logic for currency conversion. The CurrencyConverterBean is a stateless EJB bean that performs the conversion and manages the lifecycle of the bean.

Key Files:

• CurrencyConverterBean.java: Implements the currency conversion methods and lifecycle methods.

Code:

package lk.jiat.web.ejb;

import jakarta.annotation.PostConstruct;
import jakarta.annotation.PreDestroy;
import jakarta.ejb.Stateless;
import lk.jiat.web.core.remote.CurrencyConverter;

@Stateless
public class CurrencyConverterBean implements CurrencyConverter {

    private static final double USD_TO_LKR_RATE = 300.00;

    public CurrencyConverterBean() {
        System.out.println("CurrencyConverterBean Constructor called: " + this.hashCode());
    }

    @PostConstruct
    public void init() {
        System.out.println("CurrencyConverterBean Created");
    }

    @PreDestroy
    public void destroy() {
        System.out.println("CurrencyConverterBean Destroyed");
    }

    @Override
    public double convertToLKR(double amount) {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        return amount * USD_TO_LKR_RATE;
    }

    @Override
    public double convertToUSD(double amount) {
        return amount / USD_TO_LKR_RATE;
    }
}

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🌐 WebApp

The WebApp is a simple Servlet-based web application that integrates with the Core and AppModule to display the currency conversion result. It uses the CurrencyConverter EJB to convert a fixed amount of USD to LKR and displays the result on a webpage.

Key Files:

• Home.java: The main servlet that interacts with the CurrencyConverter EJB and displays results.
• index.jsp: A simple JSP page displaying the results of the conversion.

Code (Home.java):

package lk.jiat.web.servlet;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import lk.jiat.web.core.remote.CurrencyConverter;

import javax.naming.InitialContext;
import javax.naming.NamingException;
import java.io.IOException;

@WebServlet("/home")
public class Home extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html");
        response.getWriter().println("<h1>This is Home Page</h1>");

        try {
            InitialContext context = new InitialContext();
            CurrencyConverter converter = (CurrencyConverter) context.lookup("java:global/app-module/CurrencyConverterBean!lk.jiat.web.core.remote.CurrencyConverter");
            double lkr = converter.convertToLKR(1200);
            response.getWriter().println("LKR: " + lkr);
        } catch (NamingException e) {
            throw new RuntimeException(e);
        }
    }
}

Output:

This is Home Page
LKR: 360000.0

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🚀 Running the Application

Prerequisites:

1. Java 11 (or newer)
2. Maven
3. GlassFish (or any JEE compatible server)

Steps to Run:

1. Build the Projects:

   • In each project directory (Core, AppModule, WebApp), run:

     mvn clean install

2. Deploy AppModule on GlassFish:

   • Deploy the AppModule/target/app-module.war to your GlassFish server.

3. Start the WebApp:

   • Deploy the WebApp/target/webapp.war to your server.

4. Access the WebApp:

   • Open your browser and visit http://localhost:8080/webapp/home to view the results.

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🛠️ Technologies Used

• Java 11
• Jakarta EE (formerly Java EE) - for EJB, Servlets, and JNDI
• Maven - for build automation
• GlassFish - as the application server for running EJBs
• JSP - for the web interface

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📄 License

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