E-Commerce Order Processing System

Overview

This project is a basic order processing system for an e-commerce platform. It handles customer orders containing various item types, such as physical products, digital products, and gift cards. The solution focuses on object-oriented principles such as abstraction, inheritance, and polymorphism, offering a clean and extendable design.

Class Design

Core OOP Concepts

• Abstraction: The OrderItem class is an abstract class representing common attributes and methods shared among all types of order items.
• Inheritance: PhysicalProduct, DigitalProduct, and GiftCard classes extend OrderItem to inherit common behaviors while implementing specific functionalities.
• Polymorphism: Each subclass (PhysicalProduct, DigitalProduct, GiftCard) overrides methods like getTotalPrice() as needed to support different item-specific behaviors.

Class Structure

• OrderItem (abstract class):
  • Attributes: productName, price, quantity.
  • Methods: double getTotalPrice().
• PhysicalProduct:
  • Additional Attribute: shippingWeight.
  • Method: double calculateShippingCost().
• DigitalProduct:
  • Method: String generateDownloadLink().
• GiftCard:
  • Additional Attribute: recipientEmail.
  • Method: void sendGift().
• Order:
  • Attributes: orderId, customerId, List<OrderItem> items.
  • Method: void addItem(OrderItem item), double calculateTotalCost(), double calculateTotalShippingCost().
• SummaryDTO:
  • Attributes: orderId, totalCost, shippingCost, items.
  • Represents the summary of an order with all calculated costs.

Project Structure

src/main/java/com/bella/ecommerce/
├── EcommerceApplication.java
├── models/
│   ├── OrderItem.java
│   ├── PhysicalProduct.java
│   ├── DigitalProduct.java
│   ├── GiftCard.java
│   └── Order.java
├── controllers/
│   └── OrderController.java
│   └── MainController.java
├── repositories/
│   └── OrderRepository.java
│   └── OrderItemRepository.java
├── services/
│  └── OrderService.java
│  └── impl/
│     └── OrderServiceImpl.java
├── utils/
│   └── ApiResponse.java
├── exceptions/
│   └── BadRequestException.java
│   └── GlobalExceptionHandler.java
├── validators/
│   └── EmailValidator.java
│   └── TypeValidator.java
│   └── ValidEmail.java
│   └── ValidType.java
└── dtos/
    ├── CreateOrderDTO.java
    └── CreateOrderItemDTO.java
    └── OrderItemDTO.java
    └── SummaryDTO.java

API Design

1. Create a New Order

• HTTP Method: POST
• URL: /orders
• Request Body:

  {
    "customerId": "12345"
  }

  • Response:

    {
      "message": "Order created successfully",
      "status": "CREATED",
      "success": true,
      "timestamp": "2024-10-17T02:28:01.240286"
    }

2. Add Item to an Order

• HTTP Method: POST
  • URL: /orders/{orderId}/items
  • Request Body:

    {
       "type": "physical", 
       "productName": "Laptop",
       "price": 100000,
       "quantity": 2,
       "shippingWeight": 1.5
    }

• Response:

  {
    "message": "Item added to order successfully",
    "status": "CREATED",
    "success": true,
    "timestamp": "2024-10-17T02:28:01.240286"
  }

3. Retrieve Order Summary

• HTTP Method: GET
• URL: /orders/{orderId}
  • Response:

    {
        "data": {
            "customerId": "12345",
            "totalCost": 200000.0,
            "totalShippingCost": 2250.0,
            "grandTotal": 202250.0,
            "items": [
                {
                    "type": "physical",
                    "id": 1,
                    "productName": "Laptop",
                    "price": 100000.0,
                    "quantity": 2,
                    "shippingWeight": 1.5,
                    "totalPrice": 200000.0
                },
                {
                    "type": "digital",
                    "id": 2,
                    "productName": "E-book: Mastering Java",
                    "price": 15000.0,
                    "quantity": 1,
                    "totalPrice": 15000.0,
                    "downloadLink": "http://example.com/downloads/12345"
                }
            ]
        },
        "message": "Order summary retrieved successfully",
        "status": "OK",
        "success": true,
        "timestamp": "2024-10-17T02:29:09.414690"
    }

Design Decisions

1. Abstract OrderItem Class: The OrderItem class is abstract to ensure that no generic order item can be created. This ensures that every item added to an order is either a PhysicalProduct, DigitalProduct, or GiftCard, each with its own specific behavior.
2. Use of Polymorphism: The design enables flexibility when calculating the total price for each item, as each type can override the getTotalPrice() method if necessary.
3. Separation of Concerns: The OrderServiceImpl handles business logic related to order creation, item addition, and order summary retrieval, while the OrderController manages HTTP requests and responses.
4. Scalability: The use of interfaces and abstract classes ensures that new item types can be added with minimal changes to the existing code. For instance, adding a new item type like SubscriptionProduct would involve creating a new class extending OrderItem and implementing specific methods.

Testing Instructions

Setting Up the PostgreSQL Database

1. Install PostgreSQL if you haven't already, and create a database:

   CREATE DATABASE ordersystem;

2. Configure database connection in src/main/resources/application.properties:

   spring.datasource.url=jdbc:postgresql://localhost:5432/ordersystem
   spring.datasource.username=your_db_username
   spring.datasource.password=your_db_password
   spring.jpa.hibernate.ddl-auto=create
   spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect
   server.port=8090

3. Run database migrations (if using tools like Flyway or Liquibase) or allow Hibernate to create tables automatically based on your entity classes.

Cloning and Running the Application

1. Clone the repository:

   git clone https://github.com/Bellamy01/ecommerce.git
   cd ecommerce

2. Build the project using Maven:

   mvn clean install

3. Run the application:

   mvn spring-boot:run

4. The application will run on http://localhost:8090.

API Testing Using Postman and curl

1. Create a New Order

• Using Postman:

  • Method: POST
  • URL: http://localhost:8090/orders
  • Body (JSON):

    {
      "customerId": "12345"
    }

  • Click "Send" and verify the response.

• Using curl:

  curl -X POST http://localhost:8090/orders -H "Content-Type: application/json" -d '{"customerId": "12345"}'

2. Add Item to an Order

• Using Postman:

  • Method: POST
  • URL: http://localhost:8090/orders/1/items
  • Body (JSON):

    {
      "type": "PHYSICAL",
      "productName": "Laptop",
      "price": 1000.0,
      "quantity": 1,
      "shippingWeight": 2.5
    }

  • Click "Send" and verify the response.

• Using curl:

  curl -X POST http://localhost:8090/orders/1/items -H "Content-Type: application/json" -d '{"type": "PHYSICAL", "productName": "Laptop", "price": 1000.0, "quantity": 1, "shippingWeight": 2.5}'

3. Retrieve Order Summary

• Using Postman:

  • Method: GET
  • URL: http://localhost:8090/orders/1
  • Click "Send" and verify the response.

• Using curl:

  curl -X GET http://localhost:8090/orders/1

Check if app is running

Create order in Postman

Testing item creation in postman

Add item to order in postman

Retrieve order summary in postman

Conclusion

Feel free to add any additional information or context about the project here. You can discuss the challenges you faced, the lessons you learned, or the next steps you plan to take.