Ejada Bookstore Coding Assignment

This repository contains my implementation of the Bookstore Assignment for the Ejada application process. It is a Java-based RESTful API built using Spring Boot, Spring Data JPA, and an in-memory H2 database.

Below is a detailed guide of what has been implemented across the three phases, how the codebase is structured, and how you can run and test the application on your machine.

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🛠️ Tech Stack Used

• Java 21
• Spring Boot 4.1.0 (with starter packs for Web, Validation, and JPA)
• H2 Database (In-memory database for testing and local runs)
• Maven (Project build and dependency management)

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📂 How the Code is Structured

I organized the codebase into a clean, layered structure to keep concerns separated:

• com.example.bookstore: The main package containing the entry point BookstoreApplication.java.
• entity: Holds the JPA entities representing our database schema (Book and Author).
• repository: Houses our Spring Data JPA interfaces (BookRepository and AuthorRepository) which handle database interactions.
• service: Implements the business logic layer (BookService and AuthorService) to keep the controllers thin and focused.
• controller: Exposes the REST endpoints (BookController and AuthorController). As recommended in the guidelines, I used constructor-based dependency injection here instead of field injection.
• dto: Contains DTOs (BookRequest and AuthorRequest) to validate incoming payloads before they reach the persistence layers.
• exception: Holds the custom ResourceNotFoundException.
• advice: Houses the GlobalExceptionHandler to cleanly catch and structure validation errors and missing resource exceptions.

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📝 Implementation Walkthrough

Here is how I tackled the three phases of the assignment:

Phase 1: Core CRUD Operations for Books

• Developed the basic CRUD operations for managing books under /api/books (POST, GET, PUT, DELETE).
• Created a custom query finder method in the repository findByIsbn(String isbn) and exposed it on GET /api/books/isbn/{isbn} to look up books directly by their ISBN.
• Ensured correct HTTP responses (e.g., returning 204 No Content for successful deletes and 404 Not Found for missing resources on updates).

Phase 2: Centralized Exception Handling

• Set up a dedicated global controller advice (@RestControllerAdvice) to handle exceptions across all controllers.
• Intercepted MethodArgumentNotValidException to capture field-level validation errors (such as negative book prices or empty names) and output them as a clean JSON structure instead of long, confusing stack traces.
• Configured the handler to catch the custom ResourceNotFoundException and respond with a neat 404 Not Found error and a clear message.

Phase 3: Relational Data Mapping (Books & Authors)

• Implemented the Author entity with id, name, and biography.
• Configured the JPA relationship so that a Book belongs to a single Author (@ManyToOne), while an Author can write multiple Books (@OneToMany).
• Added cascade and orphan removal so that deleting an author automatically cleans up their books.
• Created independent endpoints for authors at /api/authors to manage their lifecycles.

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🌐 API Endpoint Summary

Books (/api/books)

• POST /api/books: Creates a new book (requires validation).
• GET /api/books: Retrieves a list of all books.
• GET /api/books/{id}: Retrieves a book by its database ID.
• PUT /api/books/{id}: Updates an existing book.
• DELETE /api/books/{id}: Deletes a book and returns 204 No Content.
• GET /api/books/isbn/{isbn}: Searches for a book using its ISBN.

Example Request Payload (POST /api/books):

{
  "title": "Clean Code",
  "authorId": 1,
  "isbn": "978-0132350884",
  "price": 35.99
}

Authors (/api/authors)

• POST /api/authors: Creates an author.
• GET /api/authors: Retrieves all authors.
• GET /api/authors/{id}: Retrieves a single author by ID.
• PUT /api/authors/{id}: Updates an author's info.
• DELETE /api/authors/{id}: Deletes an author.

Example Request Payload (POST /api/authors):

{
  "name": "Robert C. Martin",
  "biography": "American software engineer and author commonly known as Uncle Bob."
}

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🛡️ Input Validation Rules

• Books:
  • Title and ISBN cannot be blank.
  • Price must be positive (@Positive).
  • Author ID is required.
• Authors:
  • Name cannot be blank.

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🚨 Error Response Examples

Validation Failure (HTTP 400 Bad Request)

If you try to submit a book with a negative price or missing title, you will receive a clean error response listing the invalid fields:

{
  "errors": [
    {
      "field": "price",
      "message": "Price must be positive"
    },
    {
      "field": "title",
      "message": "Title is required"
    }
  ]
}

Resource Not Found (HTTP 404 Not Found)

If you try to request or update an ID that does not exist:

{
  "message": "Book with id 99 not found"
}

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🗄️ Database & Console

The application uses an in-memory H2 database, which makes it very lightweight and easy to run without any external database setup:

• Console URL: http://localhost:8080/h2-console
• JDBC URL: jdbc:h2:mem:bookstore
• Username: sa
• Password: (leave blank)

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⚙️ How to Build and Run the App

You can compile, test, and run the project using the included Maven wrapper.

Build and Package:

# Windows
.\mvnw.cmd clean package

# macOS/Linux
./mvnw clean package

Start the Server:

# Windows
.\mvnw.cmd spring-boot:run

# macOS/Linux
./mvnw spring-boot:run

The application will start on port 8080. You can access it at http://localhost:8080.