Prosnokorta-API (Online Quiz Management System)

📌 Project Overview

The Prosnokorta is a robust Java-based web application developed as part of the Object-Oriented Programming (OOP) course project. It serves as the backbone for managing quizzes, questions, students, and results, adhering to strict software engineering principles.

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🏗 Backend Architecture Style

We follow a Layered Architecture (MVC-inspired) to ensure separation of concerns and maintainability.

graph TD
    Controller[Controller Layer] --> Service[Service Layer]
    Service --> Repository[Repository Layer]
    Repository --> Database[(Database)]

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Each layer has a distinct responsibility:

1. Controller Layer: Handles HTTP requests and responses.
2. Service Layer: Contains business logic and transactional boundaries.
3. Repository Layer: Abstraction for data access (talks to the database).
4. Database: Persistent storage.

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� Backend Package Structure

The project follows a standard industry-grade package structure:

com.quiz
 ├── controller   # REST Endpoints
 ├── service      # Business Logic Interfaces
 │    └── impl    # Service Implementations
 ├── repository   # Data Access Interfaces
 ├── model        # JPA Entities (Domain Model)
 ├── dto          # Data Transfer Objects
 └── config       # Configuration Classes

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🧱 Backend Layer Responsibilities

3.1 Controller Layer

• Responsibility: Accept HTTP requests, validate input, call service methods, and return responses.
• Characteristics: Thin, no business logic.

@RestController
@RequestMapping("/api/student")
public class StudentController {
    // Delegates to Service Layer
}

3.2 Service Layer (OOP Core)

• Responsibility: Core business logic, transactional management.
• OOP Principles: Heavy use of Abstraction and Polymorphism.

public interface QuizService {
    int calculateScore(...);
}

@Service
public class QuizServiceImpl implements QuizService {
    // Implementation details
}

3.3 Repository Layer

• Responsibility: Database communication. (No business logic here).
• Technology: Spring Data JPA.

public interface QuizRepository extends JpaRepository<Quiz, Long> {
}

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🏛 Entity Design (Domain Model)

Entities represent real-world objects and use Inheritance and Encapsulation effectively.

Hierarchy

• User (Abstract Base Class)
  • Admin (Extends User)
  • Student (Extends User)
• Subject
• Quiz
• Question
• Result

OOP Principles Applied

• Abstraction: User is abstract; cannot be instantiated directly.
• Inheritance: Admin and Student inherit common fields (id, name, email) from User.
• Encapsulation: All fields are private with public getters/setters.
• Polymorphism: Used in service interfaces and potential user processing.

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� Database Design Principles

5.1 Normalization

• Ensures no duplicate data.
• Maintains data integrity.

5.2 Relationships

• One Subject → Many Quizzes
• One Quiz → Many Questions
• One Student → Many Results

Mapped using JPA annotations:

@OneToMany(mappedBy = "...")
@ManyToOne

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� Backend Design Principles

We adhere to SOLID principles to ensure code quality.

6.1 Single Responsibility Principle (SRP)

• Controller handles HTTP.
• Service handles Logic.
• Repository handles Data.
• Result: No "God Classes".

6.2 Open–Closed Principle (OCP)

The system is designed to be extended without modifying existing code.

• Example: Adding a new QuizType or UserRole does not break the core logic.

6.3 Dependency Injection (DI)

We use Spring's Inversion of Control (IoC) to manage dependencies, promoting loose coupling.

@Autowired
private final QuizService quizService; // Constructor Injection

6.4 Don’t Repeat Yourself (DRY)

• Shared logic is centralized in Service methods.
• Base classes reduce code duplication in Entities.

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🔒 Security by Design

Even without complex security frameworks like Spring Security (in the initial phase), the design is secure:

• Server-Side Validation: Never trust the client.
• Secure Data Flow: Correct answers are calculated on the backend and never sent to the frontend during the quiz.

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📡 API Design & Endpoints

Overview

• Base URL: /api
• Style: RESTful, JSON-based, Stateless
• Architecture: Backend-controlled logic

🔐 Part 1: Authentication APIs (Common)

Mandatory endpoints for user access.

Method	Endpoint	Purpose
POST	/api/auth/register	Create a new student account (Used by Frontend Register page)
POST	/api/auth/login	Authenticate user & identify role (Admin/Student)
POST	/api/auth/logout	End session (Logical logout)

🛠 Part 2: Admin APIs

Admin controls content (subjects, quizzes, questions), not users’ answers.

🧠 Subject Management

Method	Endpoint	Purpose
POST	/api/admin/subjects	Add new quiz subject (e.g., Math, ICT)
GET	/api/admin/subjects	View all subjects (Needed before creating quizzes)

📝 Quiz Management

Method	Endpoint	Purpose
POST	/api/admin/quizzes	Create a quiz under a subject & set duration
GET	/api/admin/quizzes/{subjectId}	View quizzes of a specific subject

❓ Question Management

Method	Endpoint	Purpose
POST	/api/admin/quizzes/{quizId}/questions	Add MCQ question to quiz
GET	/api/admin/quizzes/{quizId}/questions	Preview quiz questions (Admin view)

📊 Result Monitoring

Method	Endpoint	Purpose
GET	/api/admin/results	View all student quiz results
GET	/api/admin/results/quiz/{quizId}	View performance of students for one quiz

🎓 Part 3: Student APIs

Students consume quizzes and view their own results.

📚 Subject & Quiz Access

Method	Endpoint	Purpose
GET	/api/student/subjects	Show subject list on dashboard
GET	/api/student/quizzes/{subjectId}	Student selects quiz to attempt

🧪 Quiz Attempt Flow

Method	Endpoint	Purpose
GET	/api/student/quiz/{quizId}	Start Quiz: Fetch metadata & questions (WITHOUT correct answers)
POST	/api/student/quiz/{quizId}/submit	Submit Quiz: Backend calculates score & stores result

📈 Result Access

Method	Endpoint	Purpose
GET	/api/student/results	Student views past quiz scores
GET	/api/student/results/{resultId}	View detailed performance of one quiz

🔹 Optional API Support

• PUT /api/student/profile - Update Profile
• DELETE /api/admin/quizzes/{quizId} - Delete Quiz

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⚠️ Error Handling Strategy

• Global Exception Handling using @ControllerAdvice.
• Returns proper HTTP Status Codes (200, 400, 404, 500).
• Friendly error messages, avoiding stack trace exposure to clients.

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🎓 Academic Justification

"We followed a layered backend architecture with strong separation of concerns, ensuring clean OOP design, testability, and maintainability."

This architecture demonstrates a strong grasp of:

• Software Architecture (Layered/MVC)
• Object-Oriented Design (Inheritance, Polymorphism, Encapsulation)
• Clean Code Principles (SOLID, DRY)

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⚙️ Setup & Run Instructions

1. Clone the repository

   git clone https://github.com/your-username/online-quiz-system.git

2. Configuration
   • Create a .env file from the .env.example template:
     • Windows: copy .env.example .env
     • Linux/macOS: cp .env.example .env
   • Update .env with your MySQL database credentials.
3. Build & Run
   • Option 1: Terminal (Maven Wrapper)
     • Windows: .\mvnw spring-boot:run
     • Linux/macOS: ./mvnw spring-boot:run
   • Option 2: IDE
     • Import into IntelliJ IDEA / Eclipse.
     • Run OnlineQuizApplication.java.
4. Test Credentials The database is automatically seeded with these test accounts:
   • Admin: admin@quiz.com / admin123
   • Admin: mahadifardin@quiz.com / admin123
   • Student: student@quiz.com / student123
   • Student: fardin@quiz.com / student123

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🔗 Repository Links

• Web Frontend: https://github.com/FardinMahadi/Prosnokorta-Web
• Mobile Frontend (React Native): https://github.com/FardinMahadi/Prosnokorta-Mobile
• Backend (API): https://github.com/FardinMahadi/Prosnokorta-API

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👥 Team Members

• Mahadi Hasan Fardin (@FardinMahadi) — Team Leader Department: ICT
  University: Comilla University