PrepX Backend

A complete Full-Stack Website for Aptitude practice and practice sets. A progress report will be saved for feedback.

---

Table of Contents

• Overview
• Tech Stack
• Architecture
• Main Features
• Setup & Installation
• Project Structure
• API & Core Components
• Security
• Docker Support
• Contributing
• License

---

Overview

PrepX_Backend powers the server-side logic for the PrepX platform. It provides RESTful APIs for managing aptitude questions, user authentication (including OTP-based flows), CSV-based bulk imports, and progress tracking. The backend is built with Spring Boot and designed for security, scalability, and ease of deployment.

---

Tech Stack

• Language: Java 21
• Framework: Spring Boot 3.4+
• Database: PostgreSQL (via Spring Data JPA)
• Authentication: JWT, OTP via Email
• Build Tool: Maven
• Testing: Spring Boot Test, Spring Security Test
• CSV Handling: Apache Commons CSV
• Mail: Spring Boot Starter Mail
• Containerization: Docker

---

Architecture

• Spring Boot Application: Entry point in Application.java.
• Layered Structure: Controllers, Services, Repositories, Helpers.
• Security: Custom JWT provider, password hashing, CORS configuration.
• CSV Import: Bulk question upload and parsing.
• OTP Flow: Email-based OTP for registration/login.

---

Main Features

• User Authentication:
  • Email/password login.
  • OTP-based login and registration.
  • JWT token generation and validation.
• Question Management:
  • Bulk upload via CSV.
  • Category and difficulty filtering.
  • CRUD operations for questions.
• Email Notifications: For OTP and other communications.
• Progress Tracking: User progress and feedback.
• CORS Config: Supports multiple frontend origins.

---

Setup & Installation

Prerequisites

• Java 21+
• Maven 3.9+
• PostgreSQL database
• Docker (optional, for containerization)

Local Setup

1. Clone the Repository:

   git clone https://github.com/raja2576/PrepX_Backend.git
   cd PrepX_Backend

2. Configure Database:

   • Set your PostgreSQL URL, username, password in src/main/resources/application.properties.

3. Build the Project:

   mvn clean package

4. Run the Application:

   mvn spring-boot:run

   The API server will start on port 8080 by default.

Docker Setup

A multi-stage Dockerfile is provided for efficient builds:

• Stage 1: Uses Maven to package the app.
• Stage 2: Runs the JAR in a minimal Java runtime.

To build and run the Docker image:

docker build -t prepx-backend .
docker run -p 8080:8080 prepx-backend

---

Project Structure

PrepX_Backend/
├── Dockerfile
├── pom.xml
├── src/
│   └── main/
│       └── java/com/prepXBackend/
│           ├── Application.java        # Spring Boot entry point
│           ├── config/                 # Security, JWT, app config
│           │   ├── AppConfig.java
│           │   ├── JwtConstant.java
│           │   └── JwtProvider.java
│           ├── controller/
│           │   └── otpBasedControllerAuth.java
│           ├── helper/
│           │   └── CSVHelper.java
│           ├── model/                  # Domain models (e.g., Question, User)
│           ├── repository/             # JPA repositories
│           ├── request/
│           │   ├── LoginRequest.java
│           │   └── OtpRequest.java
│           ├── response/               # Response DTOs
│           └── service/
│               ├── EmailService.java
│               └── QuestionService.java
└── README.md

---

API & Core Components

Authentication Controller (otpBasedControllerAuth.java)

• /auth/register — Registers a new user.
• /auth/send-otp — Sends OTP to user's email.
• /auth/verify-otp — Verifies OTP for login.
• /auth/send-otp-register — Sends OTP for registration.
• /auth/verify-otp-register — Verifies OTP for registration.
• Uses JWT for secure, stateless sessions.

JWT Provider (JwtProvider.java)

• Generates and validates JWT tokens.
• Encodes email in token claims.
• Uses a base64 secret key for signing.

CSV Helper (CSVHelper.java)

• Validates CSV format.
• Parses CSV files into Question objects.
• Enables bulk import of questions via REST API.

Question Service (QuestionService.java)

• saveQuestionsFromCSV(file) — Bulk saves questions from CSV.
• getQuestionsByCategoryAndDifficulty(category, difficulty) — Fetches questions by category and difficulty.
• getAllQuestions() — Fetches all questions.

Email Service (EmailService.java)

• Sends OTPs and other emails using Spring Boot mail.

App Config (AppConfig.java)

• Configures security (BCrypt password encoder).
• Sets up CORS for multiple origins.
• Exposes headers such as Authorization.

---

Security

• Password Hashing: BCrypt.
• JWT: Custom provider for token generation and validation.
• CORS: Configured for common local and deployed frontend origins.
• OTP: Email-based OTP stored in memory for short-term use.

---

Docker Support

The provided Dockerfile supports multi-stage builds for efficient deployment. The final container exposes port 8080 and runs the compiled Spring Boot JAR.

---

Contributing

Contributions are welcome! Please fork the repo, create a feature branch, and submit a pull request.

---

License

MIT License (see LICENSE file).

---

Author

Maintained by raja2576

---

PrepX Backend: Secure, scalable aptitude practice for everyone!