![]() ![]() This makes changes time consuming and error-prone. Due to this tight coupling, any changes in the service layers will propagate to the client layer. Things can get worse if a new InvoicingService is introduced in the service layer or the existing ShippingService is updated to make the logistic part internal to the organization. Imagine the impact if the underlying data store needs to be changed to a NoSQL database or the current payment gateway is replaced with another one. It means, our clients are tightly coupled with the subsystem classes – a fundamental violation of the SOLID design principles. This is how different clients interact with the order fulfillment process of the e-commerce store.Īs you can see in the figure above, the clients need to make multiple interactions with the services implemented by subsystem classes and to do so, the clients need to be aware of the internals of the subsystem classes. Legacy desktop clients can also communicate with the store as continuing support for users who wants to place an order over the phone through a customer service assistant. Users can download the client app and place an order from their devices. Our e-commerce store also supports mobile clients. ![]() In a real e-commerce store application, the controller will typically be a specialized component of the underlying framework, such as a Spring MVC controller. When a user interacts with the UI to place an order, the request is mapped to the controller, which in turn interacts with the services to fulfill the request, and then informs the user about the fulfillment status. Shipping service: Connects with an external logistic web service to ship the product from the warehouse to the user’s address.Ī controller of the application interacts with the preceding services for an order.Payment service: Connects with a payment gateway to process the order payment.Inventory service: Checks the warehouse database running on Oracle for the availability of the product.When a user places an order for a product, the following services complete the process: In addition, clients individually interacting with the subsystem classes to fulfill a business requirement can result in a significant level of complexity.Ĭonsider an order fulfillment process of an e-commerce store. But, often dependencies between the subsystems exist. We assign specific responsibilities to the subsystem classes by following the Single Responsibility Principle. When we create a system, we divide it into subsystems to reduce complexities. In this post, we will learn about the Facade pattern and how it simplifies interactions that clients need to make with subsystem classes. We already learned about the other patterns in the structural pattern family – Adapter, Bridge, Composite, and Decorator. The Facade pattern is a part of the classic Gang of Four structural pattern family. Facade defines a higher-level interface that makes the subsystem easier to use.”ĭesign Patterns: Elements of Reusable Object-Oriented Software Facade Pattern: Introduction “ Provide a unified interface to a set of interfaces in a subsystem. ![]()
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