📚 Library Management System - Backend

This is the backend API for the Library Management System built using Spring Boot.
It provides authentication, role-based authorization, and full library management features including book borrowing with business rules.

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🚀 Technologies Used

• Java 8
• Spring Boot
• Spring Security (JWT Authentication)
• Spring Data JPA (Hibernate)
• MySQL
• Maven
• Lombok

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📂 Project Structure

com.example.LibraryManagementSystem
│
├── controller        # REST Controllers (API endpoints)
├── service           # Business Logic layer
├── repository        # JPA Repositories (Database access)
├── entity            # Database Entities
├── dto               # Data Transfer Objects
├── config            # Application & general configurations
├── security          # JWT, filters, authentication, authorization
├── exception         # Custom exceptions & global exception handling
├── enums             # Application enums (Role, Status, etc.)

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🔐 Authentication & Authorization

The system uses Spring Security with JWT.

Roles:

• ADMIN
• USER

Access Rules:

• ADMIN → Full access (manage books, authors, users)
• USER → Can borrow and return books
• Borrowing endpoints are protected with:

  @PreAuthorize("hasAnyRole('USER', 'ADMIN')")
  

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👤 User (Member)

In this system:

User acts as the library member.

There is no separate Member borrowing logic.
All borrow operations are linked to the authenticated User.

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📚 Features

✅ Author Management

• Create Author
• Update Author
• Delete Author
• Get All Authors

✅ Book Management

• Add Book
• Update Book
• Delete Book
• Get All Books
• Track available copies

✅ Borrowing Management

Business Rules:

1. A user can borrow maximum 5 books at a time.
2. Each borrowed book must be returned within 7 days.
3. A book cannot be borrowed if availableCopies = 0.
4. Same copy cannot be borrowed by multiple users simultaneously.

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🔄 Borrowing Flow

Borrow Book

Endpoint

POST /api/borrow/{userId}/{bookId}

Process

• Check user exists
• Check book exists
• Check user has less than 5 active borrowings
• Check book availability
• Create borrowing record
• Set due date = borrowDate + 7 days
• Decrease availableCopies

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Return Book

Endpoint

PUT /api/borrow/return/{borrowingId}

Process

• Check borrowing record exists
• Ensure book is not already returned
• Mark as returned
• Increase availableCopies

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🗄 Database Entities

User

• id
• username
• password
• role

Author

• id
• name

Book

• id
• title
• totalCopies
• availableCopies
• author

Borrowing

• id
• borrowDate
• dueDate
• returned
• user (ManyToOne)
• book (ManyToOne)

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🧠 Borrowing Logic (Service Layer)

• countByUserAndReturnedFalse(user) ensures max 5 books
• Due date automatically set using:

  LocalDate.now().plusDays(7);

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🛠 How to Run the Project

1️⃣ Clone Repository

git clone <your-repo-url>

2️⃣ Configure Database

Update application.properties:

spring.datasource.url=jdbc:mysql://localhost:3306/library_db
spring.datasource.username=root
spring.datasource.password=yourpassword

spring.jpa.hibernate.ddl-auto=update

3️⃣ Run Application

mvn spring-boot:run

Server runs on:

http://localhost:8080

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🧪 Testing with Postman

1. Login and get JWT token.
2. Add token to Authorization header:

Authorization: Bearer <your_token>

3. Test borrow and return endpoints.

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📌 Future Improvements

• Late return penalty system
• Borrow history endpoint
• Pagination & filtering
• Exception handling with @ControllerAdvice
• Swagger documentation

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📄 License

This project is for educational purposes.

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👨‍💻 Author

Developed as a Spring Boot practice project.