Custom Multiuser Database Management System

A lightweight, Java-based DBMS implementation with support for SQL-like queries, transaction management, and concurrency control.

Project Overview

This project implements a custom Database Management System from scratch using Java. It features a console-based interface that accepts SQL-like queries and supports multiple users with secure authentication. The system follows SOLID principles and implements core database functionalities including persistent storage, query processing, transaction management, and concurrency control.

Features

Authentication & Security

• Two-factor authentication (User ID, Password, and Captcha)
• Password hashing using SHA-256
• Password recovery system with security questions
• Comprehensive audit logging for security events

Database Operations

• Database creation and selection
• Table creation with schema definition
• Data insertion and retrieval
• SQL-like query syntax (CREATE, USE, SHOW, DESCRIBE, INSERT, SELECT)

Advanced Features

• Transaction management (BEGIN TRANSACTION, COMMIT, ROLLBACK)
• ACID compliance for data integrity
• Concurrency control with read/write locks
• In-memory indexing for optimized queries

System Architecture

The system is built with a modular architecture following SOLID principles:

• Authentication Module: Handles user authentication, password management, and security
• Storage Module: Manages persistent storage in JSON format with custom delimiters
• Query Handler: Processes SQL-like queries and executes appropriate operations
• Transaction Manager: Ensures ACID properties for transactions
• Concurrency Control: Implements read/write locks for safe multi-user access
• Index Manager: Maintains in-memory indexes for efficient data retrieval

Getting Started

Prerequisites

• Java Development Kit (JDK) 8 or higher
• Any standard Java IDE (IntelliJ IDEA, Eclipse, or NetBeans)

Running the Application

1. Clone this repository
2. Open the project in your preferred Java IDE
3. Run the Main.java file in the src/main package
4. Follow the console prompts to register or login
5. Use SQL-like commands to interact with the database

Default Credentials

• Username: admin
• Password: password

Technical Implementation Details

• Persistent Storage: Custom JSON-based storage system with efficient read/write operations
• Indexing: Tree-based in-memory indexing for optimized query performance
• Concurrency: Read/write lock mechanism to prevent data inconsistencies
• Security: SHA-256 hashing for passwords and security answers
• Transactions: Intermediate data structures to store changes before commit