🚀 Project Overview

This project is a Java-based web framework inspired by Cabin.jv framework, using Hibernate for database management and a clean architecture separating Handlers, Services, and DAOs.

🔹 Features

• 🏗 Separation of Concerns (Handlers → Services → DAOs → Database).
• 🔥 Hibernate ORM for database operations.
• 🌍 REST API for user management (CRUD operations).
• 🔧 Exception Handling with GlobalExceptionHandler.
• 📦 Singleton Pattern for SessionFactory to optimize database connections.

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📂 Project Structure

📦 cabin-demo
 ┣ 📂 src
 ┃ ┣ 📂 main
 ┃ ┃ ┣ 📂 java
 ┃ ┃ ┃ ┣ 📂 com.cabin.demo
 ┃ ┃ ┃ ┃ ┣ 📂 dao                # Database Access (DAO Layer)
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 UserDAO.java
 ┃ ┃ ┃ ┃ ┣ 📂 service            # Business Logic (Service Layer)
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 UserService.java
 ┃ ┃ ┃ ┃ ┣ 📂 handler            # API Layer (Handlers)
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 UserHandler.java
 ┃ ┃ ┃ ┃ ┣ 📂 entity             # Hibernate Entities
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 User.java
 ┃ ┃ ┃ ┃ ┣ 📂 dto                # Data Transfer Objects (DTOs)
 ┃ ┃ ┃ ┃ ┃ ┣ 📂 request
 ┃ ┃ ┃ ┃ ┃ ┃ ┗ 📜 UserRequestDTO.java
 ┃ ┃ ┃ ┃ ┃ ┣ 📂 response
 ┃ ┃ ┃ ┃ ┃ ┃ ┗ 📜 UserResponseDTO.java
 ┃ ┃ ┃ ┃ ┣ 📂 exception          # Exception Handling
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 GlobalExceptionHandler.java
 ┃ ┃ ┃ ┃ ┣ 📂 datasource         # Database Configuration
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 HibernateUtil.java
 ┃ ┃ ┃ ┃ ┣ 📂 server             # Server Setup
 ┃ ┃ ┃ ┃ ┃ ┗ 📜 HServer.java
 ┃ ┃ ┃ ┃ ┗ 📜 MainApp.java        # Application Entry Point
 ┃ ┃ ┣ 📂 resources              # Configuration Files
 ┃ ┃ ┃ ┗ 📜 hibernate.cfg.xml
 ┗ 📜 README.md                   # Documentation

✅ Separation of Concerns → Handler (Controller) → Service → DAO → Database.

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⚡️ Getting Started

1️⃣ Install Dependencies

Ensure you have:

• Java 17+
• MySQL 8.0+
• Gradle

2️⃣ Configure Database

Edit src/main/resources/hibernate.cfg.xml:

<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/cabin_db?useSSL=false</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">yourpassword</property>

Then run MySQL command:

CREATE DATABASE cabin_db;

3️⃣ Build the Project

./gradlew clean build

4️⃣ Run the Application

java -jar build/libs/cabin-demo-1.0-SNAPSHOT.jar

✅ The server will start and listen for requests.

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🌍 API Endpoints

HTTP Method	Endpoint	Description
GET	/users	Get all users
GET	/users/:id	Get user by ID
POST	/users	Create a new user
PUT	/users/:id	Update a user
DELETE	/users/:id	Delete a user

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🔹 Implementation Details

1️⃣ API Layer (UserHandler.java)

Handles HTTP requests and responses.

public class UserHandler {
    private static final UserService userService = new UserService(HibernateUtil.getSessionFactory());

    public static void getAllUsers(Request req, Response resp) {
        try {
            List<UserResponseDTO> users = userService.getAllUsers();
            resp.writeBody(ApiResponse.success(users));
        } catch (Exception e) {
            GlobalExceptionHandler.handleException(e, resp);
        } finally {
            resp.send();
        }
    }
}

✅ Delegates logic to UserService (no database access here!).

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2️⃣ Business Layer (UserService.java)

Contains business logic before calling UserDAO.

public class UserService {
    private final UserDAO userDAO;

    public UserService(SessionFactory sessionFactory) {
        this.userDAO = new UserDAO(sessionFactory);
    }

    public boolean createUser(UserRequestDTO userRequestDTO) {
        if (userRequestDTO.getName() == null || userRequestDTO.getEmail() == null) {
            throw new IllegalArgumentException("Missing required fields");
        }
        User user = new User(userRequestDTO.getName(), userRequestDTO.getEmail());
        return userDAO.save(user);
    }
}

✅ Handles validation and business rules before interacting with DAO.

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3️⃣ Persistence Layer (UserDAO.java)

Handles database interactions using Hibernate.

public class UserDAO extends BaseDAO<User> {
    public UserDAO(SessionFactory sessionFactory) {
        super(sessionFactory, User.class);
    }

    public User findByEmail(String email) {
        try (Session session = getSessionFactory().openSession()) {
            return session.createQuery("FROM User WHERE email = :email", User.class)
                    .setParameter("email", email)
                    .uniqueResult();
        }
    }
}

✅ Only handles database queries, no business logic.

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4️⃣ Exception Handling (GlobalExceptionHandler.java)

Centralized exception handling to ensure consistent error responses.

public class GlobalExceptionHandler {
    public static void handleException(Exception e, Response resp) {
        int statusCode = 500;
        String message = "Internal Server Error";

        if (e instanceof IllegalArgumentException) {
            statusCode = 400;
            message = e.getMessage();
        } else if (e instanceof NoSuchElementException) {
            statusCode = 404;
            message = "Resource not found";
        }

        resp.setStatusCode(statusCode);
        resp.writeBody(ApiResponse.error(message));
        resp.send();
    }
}

✅ Now, all API errors are handled in one place!

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⚡️ Extending the Project

1️⃣ Add More Entities

• Create a new entity in com.cabin.demo.entity.
• Create a corresponding DAO, Service, and Handler.

2️⃣ Add Authentication

• Implement AuthService for JWT authentication.
• Create AuthHandler to handle login and token verification.

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👨‍💻 Contributors

• [Your Name] - Initial Development

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📄 License

This project is licensed under the MIT License.

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