A clean Spring Boot 3 REST API for managing books, users, and the borrow/return workflow. It ships with an H2 in-memory database for quick starts, pagination on book queries, validation with helpful messages, centralized exception handling, and a built‑in HTML page to try the API in your browser — no extra tools needed.

• Tech: Spring Boot 3, Spring Web, Spring Data JPA, H2, ModelMapper, Jakarta Validation
• Java: 17
• Build: Maven
• Demo page: http://localhost:8080/api.html
• H2 Console: http://localhost:8080/h2-console (JDBC URL: jdbc:h2:mem:libdb)

• Books: create, list with pagination and text filter, get, update, delete
• Users: create and list
• Borrow / Return: record when a user borrows or returns a book
• Validation: request DTO validation with readable errors
• Exceptions: global handler for not-found and conflict scenarios
• Test Data: preloaded users and books via data.sql
• API Demo: simple HTML page to call endpoints from the browser

Prerequisites

• Java 17
• Maven 3.9+

Run locally

• mvn spring-boot:run
• Open http://localhost:8080/api.html to try the API in your browser
• H2 console: http://localhost:8080/h2-console
  • JDBC URL: jdbc:h2:mem:libdb
  • User: sa, Password: (empty)

Main class

• src/main/java/org/masumjia/librarymanagementsystem/LibrarySystemManagementApplication.java

Configuration

• src/main/resources/application.properties
  • In-memory H2 database, schema auto-update, SQL logged
  • H2 web console enabled at /h2-console

Base path: /api

Books

• Create: POST /api/books
• List (paginated): GET /api/books?q={text}&page={0..}&size={1..}
• Get: GET /api/books/{id}
• Update: PUT /api/books/{id}
• Delete: DELETE /api/books/{id}

Users

• Create: POST /api/users
• List: GET /api/users

Borrowing

• Borrow: POST /api/borrow/{bookId}/user/{userId}
• Return: POST /api/return/{bookId}/user/{userId}

• Create a book:
  • curl -X POST http://localhost:8080/api/books -H "Content-Type: application/json" -d '{"title":"Clean Architecture","author":"Robert C. Martin","isbn":"ISBN-999"}'
• List books (page 0, size 10, filter by “Clean”):
  • curl "http://localhost:8080/api/books?q=Clean&page=0&size=10"
• Borrow a book:
  • curl -X POST http://localhost:8080/api/borrow/1/user/1
• Return a book:
  • curl -X POST http://localhost:8080/api/return/1/user/1

Seed data (src/main/resources/data.sql):

• Users: Alice, Bob
• Books: Clean Code, Effective Java, Spring in Action

Entities

• User(id, name, email)
• Book(id, title, author, isbn, available)
• BorrowRecord(id, book_id, user_id, borrowed_at, returned_at)

DTOs and Requests

• CreateUserRequest, UserDto
• CreateBookRequest, UpdateBookRequest, BookDto

• BookController (/api/books): CRUD + pagination
• UserController (/api/users): create + list
• BorrowController (/api): borrow/return endpoints

Global error handling is implemented via GlobalExceptionHandler that returns a structured ApiError payload.

Build

• mvn clean package

Run

• mvn spring-boot:run

Test

• mvn test
• Unit tests:
  • src/test/java/org/masumjia/librarymanagementsystem/service/BookServiceTest.java
  • src/test/java/org/masumjia/librarymanagementsystem/service/BorrowServiceTest.java

• src/main/java/.../controller — REST controllers
• src/main/java/.../service — business logic
• src/main/java/.../repository — Spring Data JPA repositories
• src/main/java/.../entity — JPA entities
• src/main/java/.../dto — request/response models
• src/main/java/.../exception — custom exceptions + handler
• src/main/java/.../util — helpers (e.g., pagination wrapper)
• src/main/resources/static/api.html — in‑browser API tester
• src/main/resources/data.sql — seed data

• Uses in‑memory H2; data resets on restart. For persistence, switch to a real DB in application.properties.
• Pagination defaults: page=0, size=10, optional q filter on title/author.