This E-Commerce application allows users to add items to a cart and going through a checkout, buying the items based on available inventory. Complete with user interface using JFrame.
This project was proposed to my team and I by my introduction to object-oriented programming class during my studies at Carleton University. It was my first exposure to Java as a language and the idea of object-oriented programming. The goal was to create a basic shopping application complete with a user interface and inventory.
I did not know this while completing the project, but in the later stages of my degree, I’ve realized this project follows a modified Model View Controller (MVC) architecture and the classes are broken down as such:
However, we did not extrapolate the actions or controller class from the view as we had not learned about it yet.
A Product is a simple class containing a name, an identification number, and a price. It only contains getters as these attributes can only be set with the constructor. The price and id can’t be less than one.
The interface was made in the ProductStockContainer class and set methods that needed to be used by any class that implemented it. All classes implementing it needs to have a getProductQuantity(), an addProductQuantity(), a removeProductQuantity(), and a getNumOfProducts(). This is to ensure that Products can be added and removed from the Inventory as well as the ShoppingCart.
The Inventory is a container that holds all the different Products as well as their quantity. It implements the ProductStockContainer interface, meaning it must implement the four methods listed above. There can also be a case where the store has a Product but has not quantity left.
The ShoppingCart extends Inventory, using all its methods and implementing ProductStockContainer as well. It is a sub-class of Inventory as customers need the ability to add Products to their carts, creating their own sub-Inventory.
The StoreManager (model) contains all the business logic of the system. It draws upon and manipulates the Inventory, adding or removing Product. It also can add Product to the ShoppingCart, by removing Product from the Inventory and adding it to a customer’s ShoppingCart. If the customer does not checkout with those Products, they are removed from the ShoppingCart and adding back to the Inventory for other customers to purchase.
The StoreView (view and controller) contains all the rendering for the user interface using Swing. Since we had not learned about the MVC architecture yet, the action buttons (controller portion) for when a customer adds, removes, or checks out with Products are also included in this file. It also contains a reference to the StoreManager so that the action buttons can call its methods when a customer clicks them.
We began by creating a basic store with the StoreManager, Product, and Inventory. To use all the functionality, we set a main() method in StoreManager that created Product, added it to the Inventory. In the main() method, we also used the StoreManager to add, remove, and return various lists of Product.
We then implemented the ProductStockContainer interface so that any class that implemented it needed to have the four get, add, and remove methods. We then made Inventory implement this interface as going forward we would need it to follow this interface.
Following the creation of the interface, we created the ShoppingCart which we made extend Inventory and implement ProductStockContainer so that customers were able to add and remove Product from their cart. We continued using the main() method, now adding the ShoppingCart functionalities.
Finally, we created the StoreView class using Swing so that the customer would be able to view and purchase various items with buttons. We then moved the main() method into StoreView as it needed to render the user interface. It created an instance of the StoreManager which automatically creates an instance of Inventory, and four products that customers could purchase. In our case, our store was a bookstore, so we sold textbooks for four of our classes. Finally, it created a StoreView instance and rendered the user interface, including photos.
Overall, this project was very fun! It was the first time that I was exposed to object-oriented programming, and I absolutely loved it. The way I was able to separate each of the classes and instances so that it didn’t look like or feel like spaghetti code amazed me.
Additionally, I learned a lot about creating basic user interfaces using Swing, which is something that intrigued me as I was always curious as to how developers made user interfaces attached to pieces of software.
Looking back at the project, I would separate the StoreView class into a view which only renders the user interface and a controller which handles all the button actions. I would also potentially separate the StoreView into different parts of the user interface so that the code is easier to read.
