📚 Library Management API (Spring Boot + PostgreSQL)

A simple and clean Library Management System built using Java, Spring Boot, and PostgreSQL. This API allows you to:

• Manage books
• Manage borrowers
• Borrow and return books
• Track lending records
• View borrowing history

Everything is built with simplicity so anyone can easily set up, understand, and use the API.

🚀 Features

✅ Book Management

• Add new books
• Update book details
• Delete books
• Get a single book
• Get all books
• Search books by title, author, or ISBN

👤 Borrower Management

• Register borrowers
• Update borrower details
• Delete borrowers
• View single borrower
• List all borrowers

🔁 Lending / Borrowing

• Borrow a book
• Return a book
• View borrowing history
• View currently borrowed books

🏗️ Project Architecture

src/main/java └── com.pl.librarymanagement ├── controller → Handles API endpoints ├── service → Main business logic ├── dto → Data Transfer Objects ├── entity → JPA Entities (Books, Borrowers, Lending Records) └── repository → JPA Repositories for DB access

This structure keeps the project clean, modular, and easy to extend.

🗂️ Database Structure

Your PostgreSQL database contains 3 tables:

📘 books

Column	Type	Description
id	bigserial PK	Auto-generated
title	varchar	Book title
author	varchar	Author name
isbn	varchar unique	Unique book identifier
total_copies	int	Total copies in library
available_copies	int	Currently available copies

👤 borrowers

Column	Type	Description
id	bigserial PK
name	varchar
email	varchar unique
member_id	varchar unique

🔁 lending_records

Column	Type	Description
id	bigserial PK
book_id	FK → books
borrower_id	FK → borrowers
borrowed_at	date
due_date	date
returned_at	date nullable

🔗 ER Diagram (Text Version)

Borrower (1) ----- (M) LendingRecord (M) ----- (1) Book

Meaning:

• A borrower can borrow many books
• A book can be borrowed many times
• Every borrowing action creates a lending record

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API Documentation

This project includes a Postman collection for API documentation and testing.

Location: postman/library-management.postman_collection.json

To use:

1. Open Postman
2. Click Import
3. Select the JSON file
4. Run the requests

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📦 API JSON Examples

This section shows the JSON format for all major endpoints in the API.

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📘 BOOK ENDPOINTS (/api/books)

---

1️⃣ Create Book — POST /api/books

✅ Request Body (BookRequest)

{
  "title": "Clean Code",
  "author": "Robert Martin",
  "isbn": "9780132350884",
  "totalCopies": 10
}

✅ Response (BookResponse)

{
  "id": 1,
  "title": "Clean Code",
  "author": "Robert Martin",
  "isbn": "9780132350884",
  "totalCopies": 10,
  "availableCopies": 10
}

---

2️⃣ Update Book — PUT /api/books/{id}

Request Body

{
  "title": "Clean Code (Updated Edition)",
  "author": "Robert Martin",
  "totalCopies": 12,
  "availableCopies": 8
}

---

3️⃣ Search Books Example

GET /api/books/search/title?title=clean

Response:

[
  {
    "id": 1,
    "title": "Clean Code",
    "author": "Robert Martin",
    "isbn": "9780132350884",
    "totalCopies": 10,
    "availableCopies": 5
  }
]

---

👤 BORROWER ENDPOINTS (/api/borrowers)

---

1️⃣ Create Borrower — POST /api/borrowers

Request Body

{
  "name": "John Doe",
  "email": "john.doe@gmail.com",
  "memberId": "MBR001"
}

Response

{
  "id": 1,
  "name": "John Doe",
  "email": "john.doe@gmail.com",
  "memberId": "MBR001"
}

---

2️⃣ Update Borrower — PUT /api/borrowers/{id}

Request Body

{
  "name": "John Doe Updated",
  "email": "updated.john@gmail.com"
}

---

🔁 LENDING ENDPOINTS (/api/lending)

---

1️⃣ Borrow Book — POST /api/lending/borrow

Request Body (BorrowRequest)

{
  "bookId": 1,
  "borrowerId": 3
}

Response (LendingRecordResponse)

{
  "id": 12,
  "bookId": 1,
  "bookTitle": "Clean Code",
  "borrowerId": 3,
  "borrowerName": "John Doe",
  "borrowedAt": "2025-01-12",
  "dueDate": "2025-01-26",
  "returnedAt": null
}

---

2️⃣ Return Book — POST /api/lending/return

Request Body (ReturnBookRequest)

{
  "lendingRecordId": 12
}

Response

{
  "id": 12,
  "bookId": 1,
  "bookTitle": "Clean Code",
  "borrowerId": 3,
  "borrowerName": "John Doe",
  "borrowedAt": "2025-01-12",
  "dueDate": "2025-01-26",
  "returnedAt": "2025-01-18"
}

---

3️⃣ Borrower History — GET /api/lending/history/{borrowerId}

Response

[
  {
    "id": 12,
    "bookTitle": "Clean Code",
    "borrowedAt": "2025-01-12",
    "dueDate": "2025-01-26",
    "returnedAt": "2025-01-18"
  },
  {
    "id": 13,
    "bookTitle": "Atomic Habits",
    "borrowedAt": "2025-02-01",
    "dueDate": "2025-02-15",
    "returnedAt": null
  }
]

---

4️⃣ Currently Borrowed — GET /api/lending/current

Response

[
  {
    "id": 13,
    "bookId": 2,
    "bookTitle": "Atomic Habits",
    "borrowerId": 1,
    "borrowerName": "John Doe",
    "borrowedAt": "2025-02-01",
    "dueDate": "2025-02-15",
    "returnedAt": null
  }
]

---

🧪 Endpoints Summary

📘 Book Endpoints (/api/books)

Method	Endpoint	Description
POST	/api/books	Add a book
PUT	/api/books/{id}	Update book info
DELETE	/api/books/{id}	Delete book
GET	/api/books/{id}	Get one book
GET	/api/books	Get all books
GET	/api/books/search/title	Search by title
GET	/api/books/search/author	Search by author
GET	/api/books/search/isbn	Search by ISBN

👤 Borrower Endpoints (/api/borrowers)

Method	Endpoint	Description
POST	/api/borrowers	Register borrower
PUT	/api/borrowers/{id}	Update borrower
DELETE	/api/borrowers/{id}	Delete borrower
GET	/api/borrowers/{id}	Get borrower
GET	/api/borrowers	List all borrowers

🔁 Lending Endpoints (/api/lending)

Method	Endpoint	Description
POST	/api/lending/borrow	Borrow a book
POST	/api/lending/return	Return a book
GET	/api/lending/history/{borrowerId}	Borrower history
GET	/api/lending/current	Currently borrowed books

🔧 How the API Works (Simple Explanation)

1️⃣ Adding Books

When you add a book, you provide title, author, ISBN, and total copies. The system automatically sets available copies equal to total copies.

2️⃣ Registering Borrowers

Borrowers must have a name, email, and member ID. Emails and member IDs are unique.

3️⃣ Borrowing a Book

The API:

1. Checks if the book exists

2. Checks if the borrower exists

3. Confirms the book has available copies

4. Reduces available copies by 1

5. Creates a lending record with:

   • borrowed_at = today
   • due_date = today + 14 days
   • returned_at = null

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4️⃣ Returning a Book

The API:

1. Retrieves the lending record
2. Marks returned_at as today
3. Increases book’s available copies by 1

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5️⃣ Viewing Borrowing History

Shows all books a borrower ever borrowed — both returned and currently borrowed.

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6️⃣ Viewing Currently Borrowed Books

Shows all lending records where returned_at is NULL.

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⚙️ Running the Project

Requirements

• Java 17+
• Maven
• PostgreSQL installed
• pgAdmin (optional)

Setup

1. Create PostgreSQL database:

   CREATE DATABASE librarydb;
   

2. Update application.properties:

   spring.datasource.url=jdbc:postgresql://localhost:5432/librarydb
   spring.datasource.username=postgres
   spring.datasource.password=YOUR_PASSWORD
   spring.jpa.hibernate.ddl-auto=update
   spring.jpa.show-sql=true
   

3. Run the project:

   mvn spring-boot:run
   

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🐳 Optional: Container Support

If you cannot run Docker, you can use Podman. It works exactly like Docker.

Example:

podman run -d -p 5432:5432 -e POSTGRES_PASSWORD=1234 postgres

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🤝 Contributing

If you want to improve:

• Add transaction logs
• Add email notifications
• Add admin roles
• Add fine/penalty for overdue books

PRs are welcome

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📜 License

This project is free to use and modify.

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