Library Management System using Spring Boot

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In this tutorial, we will learn how to build REST APIs for a Library Management System Project using Spring Boot, Spring Data JPA (Hibernate), and MySQL database.

We'll create a simple version of the Library Management System with basic functionalities: 
  1. Create a new User
  2. Fetch all the Users
  3. Add new book
  4. Fetch all the books
  5. Fetch specific book
  6. Delete a book 
  7. Borrow a book 
  8. Return a book

1. Set up a Spring Boot project

Let's launch Spring Initializr and fill up the following project details: 

Project: Maven Project (or Gradle) 

Language: Java 

Packaging: Jar 

Java version: 17

Dependencies: Spring Web, Spring Data JPA, MySQL Driver, and Lombok

Download, extract the project, and import to your favorite IDE.

2. Configure the MySQL database 

Let's open the src/main/resources/application.properties file and add the MySQL configuration properties:

spring.datasource.url=jdbc:mysql://localhost:3306/banking_app
spring.datasource.username=root
spring.datasource.password=Mysql@123
spring.jpa.hibernate.ddl-auto=update

Make sure that you change the MySQL database username and password as per your MySQL installation on your machine.

The spring.jpa.hibernate.ddl-auto=update line ensures that tables and columns get automatically created or updated based on your JPA entities.

3. Create JPA Entities

User

Let's create a User JPA entity and add the following code to it:
import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
@Entity
public class User {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
}

Book

Let's create a Book JPA entity and add the following code to it:
import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
@Entity
public class Book {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;
    private String author;
    private boolean borrowed;
    @ManyToOne
    @JoinColumn(name = "user_id")
    private User borrowedBy;
}

We added a relationship between the Book and User entities to track which user has borrowed a book.

4. Create Spring Data JPA Repositories

Next, let's create Spring Data JPA repositories to get CRUD methods to perform CRUD database operations on Book and User entities.

BookRepository

import net.javaguides.bankingapp.entity.Book;
import org.springframework.data.jpa.repository.JpaRepository;

public interface BookRepository extends JpaRepository<Book, Long> {
}

UserRepository

import net.javaguides.bankingapp.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;

public interface UserRepository extends JpaRepository<User, Long> {
}

6. Create a Service Layer

BookService

import net.javaguides.bankingapp.entity.Book;
import net.javaguides.bankingapp.entity.User;
import net.javaguides.bankingapp.repository.BookRepository;
import net.javaguides.bankingapp.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class BookService {

    @Autowired
    private BookRepository bookRepository;

    @Autowired
    private UserRepository userRepository;

    public List<Book> findAll() {
        return bookRepository.findAll();
    }

    public Book findById(Long id) {
        return bookRepository.findById(id).orElse(null);
    }

    public Book save(Book book) {
        return bookRepository.save(book);
    }

    public void deleteById(Long id) {
        bookRepository.deleteById(id);
    }

    public Book borrowBook(Long bookId, Long userId) {
        Book book = findById(bookId);
        User user = userRepository.findById(userId).orElse(null);

        if (book != null && !book.isBorrowed() && user != null) {
            book.setBorrowedBy(user);
            book.setBorrowed(true);
            return save(book);
        }
        // Handle errors (e.g., book not found, book already borrowed, user not found)
        return null;
    }

    public Book returnBook(Long bookId) {
        Book book = findById(bookId);
        if (book != null && book.isBorrowed()) {
            book.setBorrowedBy(null);
            book.setBorrowed(false);
            return save(book);
        }
        // Handle errors (e.g., book not found, book not borrowed)
        return null;
    }
}

UserService

import net.javaguides.bankingapp.entity.User;
import net.javaguides.bankingapp.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public List<User> findAll() {
        return userRepository.findAll();
    }

    public User save(User user) {
        return userRepository.save(user);
    }
}

7. Controller Layer

UserController

Let's create a UserController class and expose a couple of REST APIs to save and fetch all users.
import net.javaguides.bankingapp.entity.User;
import net.javaguides.bankingapp.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/users")
public class UserController {
    @Autowired
    private UserService userService;

    @GetMapping
    public List<User> getAllUsers() {
        return userService.findAll();
    }

    @PostMapping
    public User addUser(@RequestBody User user) {
        return userService.save(user);
    }
}

BookController

Let's create BookController class and expose REST APIs to save, fetch, fetch all, delete, barrow, and return books.
import net.javaguides.bankingapp.entity.Book;
import net.javaguides.bankingapp.service.BookService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/api/books")
public class BookController {

    @Autowired
    private BookService bookService;

    @GetMapping
    public List<Book> getAllBooks() {
        return bookService.findAll();
    }

    @GetMapping("/{id}")
    public Book getBook(@PathVariable Long id) {
        return bookService.findById(id);
    }

    @PostMapping
    public Book addBook(@RequestBody Book book) {
        return bookService.save(book);
    }

    @PutMapping("/{id}")
    public Book updateBook(@PathVariable Long id, @RequestBody Book book) {
        // Additional logic to ensure you're updating the correct book
        return bookService.save(book);
    }

    @DeleteMapping("/{id}")
    public void deleteBook(@PathVariable Long id) {
        bookService.deleteById(id);
    }

    @PostMapping("/{bookId}/borrow/{userId}")
    public ResponseEntity<Book> borrowBook(@PathVariable Long bookId, @PathVariable Long userId) {
        Book borrowedBook = bookService.borrowBook(bookId, userId);
        if (borrowedBook != null) {
            return ResponseEntity.ok(borrowedBook);
        } else {
            return ResponseEntity.badRequest().build(); // or a more descriptive error response
        }
    }

    @PostMapping("/{bookId}/return")
    public ResponseEntity<Book> returnBook(@PathVariable Long bookId) {
        Book returnedBook = bookService.returnBook(bookId);
        if (returnedBook != null) {
            return ResponseEntity.ok(returnedBook);
        } else {
            return ResponseEntity.badRequest().build(); // or a more descriptive error response
        }
    }
}

Run and Test the Spring Boot Application

Navigate to the main application class (with @SpringBootApplication annotation) and run it as a Java application.

Add a new user: 

HTTP Method: POST 
URL: http://localhost:8080/api/users 

Fetch all users: 

HTTP Method: GET 
URL: http://localhost:8080/api/users

Add a new book: 

HTTP Method: POST 
URL: http://localhost:8080/api/books

Fetch all books: 

HTTP Method: GET 
URL: http://localhost:8080/api/books

Fetch a specific book: 

HTTP Method: GET 
URL: http://localhost:8080/api/books/{id} (Replace {id} with the book's ID.)

Update a book: 

HTTP Method: PUT 
URL: http://localhost:8080/api/books/{id} (Replace {id} with the book's ID.)

Delete a book: 

HTTP Method: DELETE 
URL: http://localhost:8080/api/books/{id} (Replace {id} with the book's ID.)

Borrow a book: 

HTTP Method: POST 
URL: http://localhost:8080/api/books/{bookId}/borrow/{userId}

Return a book: 

HTTP Method: POST 
URL: http://localhost:8080/api/books/{bookId}/return (Replace {bookId} with the book's ID.)


GitHub

The source code of this tutorial is available on my GitHub repository: library-management-system

Conclusion

In this tutorial, we have built the following REST APIs for a Library Management System Project using Spring Boot, Spring Data JPA (Hibernate), and MySQL database.
  1. Create a new User
  2. Fetch all the Users
  3. Add new book
  4. Fetch all the books
  5. Fetch specific book
  6. Delete a book 
  7. Borrow a book 
  8. Return a book

Related Spring and Spring Boot Tutorials/Guides:

Spring Boot Tutorials [500+] Spring Boot Testing Tutorial Spring Boot Microservice Tutorial Spring Boot Kafka Microservices Spring Boot + Apache Kafka Tutorial Spring Core Tutorial Spring MVC Tutorial Spring Data JPA Tutorial Spring Framework for Beginners Spring AOP Tutorial Spring Security Tutorial Spring Exceptions Tutorial Spring Boot Interview Questions Spring Boot Microservices Interview Questions Apache Kafka Tutorials Docker Tutorials and Guides Spring Boot RabbitMQ Tutorials Angular CRUD Example with Spring Boot Spring Boot + Angular 12 CRUD Full Stack Spring Boot + Angular 8 CRUD Full Stack Spring Boot + Angular 10 CRUD Full Stack Spring Boot + React JS CRUD Full Stack React JS ( React Hooks) + Spring Boot Spring Boot Thymeleaf CRUD Full Stack Spring Boot User Registration and Login Node Js + Express + MongoDB CRUD Vue JS + Spring Boot REST API Tutorial

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