Class Diagram for Online Shopping System

A UML class diagram for online shopping system is used to represent, explain, and document the parts (classes) of an online shopping system. It can also be a reference or way to create executable software code. Class diagrams provide an overview of the online shopping’s classes, functions, and relationships.

Project Overview

What is an Online Shopping?

Online shopping is the same as e-commerce software which also provides functions similar to e-commerce. This kind of platform enables customers to shop online by browsing their sites or mobile apps. It also provide a page that displays different kinds of shopping products.

Additionally, this also allows sellers to display their goods on their sites and sell their products. In short, the online shopping system involves products, customers, and sellers doing their trading online.

What is a Class Diagram?

A UML class diagram for online shopping is crucial and useful for system development. This is because the class diagrams are very effective in showing the system’s structure in detail, including the structures of each class. This works best with other Online Shopping System UML Diagrams.

Additionally, the class diagram blueprints show how things in the system work and are related. It also shows the system’s activities and the services it provides. Therefore, a class diagram defines the physical components of a system and can directly relate to object-oriented languages.

Online Shopping System UML Class Diagram

This simple class diagram for online shopping gives you the exact details about the system’s class characteristics and methods. It also clarifies the connections of classes in the system.

Here, I will be showing you the sample constructed class diagram provided with its attributes and methods. This is constructed with the simple idea derived from the common function of online shopping.

The illustration shows a simple idea of how the class diagram works. It resembles a flowchart in which classes are shown in boxes with three rectangles in each. The top rectangle has the class’s name; the middle holds the class’s properties, and the bottom contains the class’s methods.

The classes identified for Online Shopping System were the items, customer, seller, order, delivery, and transaction. Their roles are in the middle part and called their attributes. The function of each class is in its’ methods.

You can edit this diagram and it is up to you how will you create your class diagram. However, you need to be precise with your information and consider the decisions included.

Downloadable Pdf File

Online Shopping System Class Diagram in Java (2026 Code Example)

Below is a complete Java implementation following the Class Diagram structure. You can copy these classes directly into your capstone project as a starting point:

Customer Class

import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class Customer {
    private String customerId;
    private String name;
    private String email;
    private String address;
    private List<Transaction> transactions;

    public Customer(String customerId, String name, String email, String address) {
        this.customerId = customerId;
        this.name = name;
        this.email = email;
        this.address = address;
        this.transactions = new ArrayList<>();
    }

    public void placeOrder(Product product, int quantity) {
        Transaction transaction = new Transaction(this, product, new Date(), quantity);
        transactions.add(transaction);
    }

    public List<Transaction> getTransactions() {
        return transactions;
    }
}

Product Class

public class Product {
    private String productId;
    private String name;
    private String category;
    private double price;
    private int stockQuantity;

    public Product(String productId, String name, String category, double price, int stockQuantity) {
        this.productId = productId;
        this.name = name;
        this.category = category;
        this.price = price;
        this.stockQuantity = stockQuantity;
    }

    public void reduceStock(int quantity) {
        this.stockQuantity -= quantity;
    }

    public void increaseStock(int quantity) {
        this.stockQuantity += quantity;
    }
}

Transaction Class

import java.util.Date;

public class Transaction {
    private Customer customer;
    private Product product;
    private Date transactionDate;
    private int quantity;

    public Transaction(Customer customer, Product product, Date transactionDate, int quantity) {
        this.customer = customer;
        this.product = product;
        this.transactionDate = transactionDate;
        this.quantity = quantity;
    }

    public void updateQuantity(int quantity) {
        this.quantity = quantity;
    }
}

Online Shopping System Class Diagram in PHP (2026 Code Example)

Here’s the same Class Diagram implemented in modern PHP 8.x. This pattern works well for Laravel and CodeIgniter capstones:

Customer.php

<?php

class Customer {
    private string $customerId;
    private string $name;
    private string $email;
    private string $address;
    private array $transactions = [];

    public function __construct(
        string $customerId,
        string $name,
        string $email,
        string $address
    ) {
        $this->customerId = $customerId;
        $this->name = $name;
        $this->email = $email;
        $this->address = $address;
    }

    public function placeOrder(Product $product, int $quantity): void {
        $this->transactions[] =
            new Transaction($this, $product, new DateTime(), $quantity);
    }

    public function getTransactions(): array {
        return $this->transactions;
    }
}

Product.php

<?php

class Product {
    private string $productId;
    private string $name;
    private string $category;
    private float $price;
    private int $stockQuantity;

    public function __construct(
        string $productId,
        string $name,
        string $category,
        float $price,
        int $stockQuantity
    ) {
        $this->productId = $productId;
        $this->name = $name;
        $this->category = $category;
        $this->price = $price;
        $this->stockQuantity = $stockQuantity;
    }

    public function reduceStock(int $quantity): void {
        $this->stockQuantity -= $quantity;
    }

    public function increaseStock(int $quantity): void {
        $this->stockQuantity += $quantity;
    }
}

Transaction.php

<?php

class Transaction {
    private Customer $customer;
    private Product $product;
    private DateTime $transactionDate;
    private int $quantity;

    public function __construct(
        Customer $customer,
        Product $product,
        DateTime $transactionDate,
        int $quantity
    ) {
        $this->customer = $customer;
        $this->product = $product;
        $this->transactionDate = $transactionDate;
        $this->quantity = $quantity;
    }

    public function updateQuantity(int $quantity): void {
        $this->quantity = $quantity;
    }
}

UML Class Diagram Symbols, Complete Reference Table

Use this reference table to read or draw any UML Class Diagram correctly. These symbols are standard across all UML modeling tools:

Quick rule: If you’re unsure between aggregation and composition, ask: “If I destroy the whole, does the part still exist?” Yes = aggregation. No = composition.

How to Draw Online Shopping System Class Diagram, Step by Step

Step 1, Open draw.io

Go to app.diagrams.net → create blank diagram → enable UML shapes.

Step 2, Draw Customer class

Customer

• customerId: String
• name: String
• email: String
• address: String

Methods:

• placeOrder(product: Product, quantity: int): void
• getTransactions(): List

Step 3, Draw Product class

Product

• productId: String
• name: String
• category: String
• price: double
• stockQuantity: int

Methods:

• reduceStock(quantity: int): void
• increaseStock(quantity: int): void

Step 4, Draw Transaction (Association Class)

Transaction

• transactionDate: Date
• quantity: int

Method:

• updateQuantity(quantity: int): void

Transaction connects Customer ↔ Product and records purchases.

Step 5, Draw relationships

• Customer → Transaction (1 to 0..*)
• Product → Transaction (1 to 0..*)
• Customer → Product (Association, 1 to 0..*)

Step 6, Add multiplicity

Always label:

• Customer: 1 → Transactions: 0..*
• Product: 1 → Transactions: 0..*

Export

• PNG (minimum 1200px width) for presentation
• PDF for documentation

💡 Pro tip: draw.io is completely free and our top pick. If you need more advanced features (auto-layout, version history, team collaboration), Lucidchart has a powerful UML tool with a free tier that’s sufficient for most capstone projects.

Common Mistakes in Online Shopping System Class Diagrams

Mistake #1, Treating Transaction as just order history

Transaction is not just logs; it is an association class between Customer and Product.

Mistake #2, Missing multiplicity

Always include:

• Customer 1 → 0..* Transactions
• Product 1 → 0..* Transactions

Mistake #3, Confusing stock logic with database logic

Stock management belongs in Product class using:

• reduceStock()
• increaseStock()

Not in database-only thinking.

Mistake #4, Wrong use of composition

Customer does NOT own Product.

Products exist independently and are shared across customers.

Use association, not composition.

Mistake #5, Empty classes

Each class must have behavior:

Customer → placeOrder()
Product → manage stock
Transaction → record purchase

Mistake #6, Low-quality export

Always export:

• PNG ≥ 1200px
• PDF for submission

Blurry diagrams are a common defense issue.

Check out the articles linked and suggested below to find out more about Diagrams and other topics.

• Class Diagram for Online Shopping Cart
• Online Shopping Cart UML Diagram
• UML Diagrams for Online Shopping System
• Component Diagram for Online Shopping System
• Online Shopping System Complete UML Diagrams
• Online Shopping Cart Class Diagram
• Activity Diagram for Online Shopping System

Conclusion

The class diagram is a modeled diagram that explains systems classes and relationships. It can depict the names and attributes of classes, as well as their links and methods that make up the software.

Moreover, the class diagram is the most essential type of UML diagram and is critical in software development. It is an approach to showing the system’s structure in detail and part by part.

Inquiries

If you have inquiries or suggestions about the Class Diagram discussion, just leave us your comments below. We would be glad to hear to concerns and be part of your learning.

Working online shopping source code that implements this diagram

The diagram above defines the flows; these are the actual online shopping systems on itsourcecode.com that implement them. Pick one in your team’s stack and you have a working reference to point your panel at when they ask “show me where this flow actually runs in code.”

PHP: E-commerce Website in PHP

Vanilla PHP + MySQL. Customer, Product, Cart, Order classes map directly to tables.

Laravel (PHP): Complete Laravel E-commerce

Laravel 10 + Tailwind. Eloquent models = your class diagram in Laravel form.

CodeIgniter (PHP): Complete E-commerce in CodeIgniter

CI4 + Bootstrap. MVC structure mirrors the class boundaries in your UML.

ASP.NET: E-commerce Website in ASP.NET

ASP.NET MVC + SQL Server. Classic capstone-ready stack for Microsoft-track schools.

Django (Python): Django E-commerce

Django 4 + Bootstrap. Django models map cleanly to your class diagram entities.

Python (Flask): Online Shopping in Python

Python + Flask + SQLite. Lightweight option for beginners and demo systems.

Vue.js + Firebase: Vue.js + Firebase Shopping Cart

Vue 3 + Firebase realtime DB. Modern SPA, good for “cloud data store” defense angle.

How to use this for your Chapter 3 (Methodology): download the project in your stack, then map each process and data store in this diagram to a specific module, controller, or table in the downloaded source. That mapping IS the bridge between your design chapter and your implementation chapter, the single thing panels want to see traced end to end.

Mary Grace G. Patulada

Programmer & Technical Writer at PIES IT Solution

Mary Grace G. Patulada (pen name ‘Nym’) is a programmer and writer at PIES IT Solution with a BSIT background from Carlos Hilado Memorial State College, Binalbagan Campus. Authored 370+ UML diagram tutorials and capstone documentation guides at itsourcecode.com. Specializes in UML (class, use case, activity, sequence, component, deployment), DFD, and ER diagrams for BSIT capstone projects.

Expertise: UML Diagrams · DFD · ER Diagrams · Use Case Diagrams · Activity Diagrams · Capstone Documentation · PHP  · View all posts by Mary Grace G. Patulada →