Model-view-controller design pattern tutorial
The model-view-controller design pattern asserts that the development of any nontrivial application is simplified if it's partitioned into three loosely coupled pieces:
- A controller that handles incoming requests.
- A model that holds the data pertinent to handling the request.
- A view component that handles rendering.
How does MVC work?
The principle behind the model-view-controller (MVC) design pattern is quite simple:
- The controller handles incoming requests and puts any data the client needs into a component called a model.
- When the controller's work is done, the model is passed to a view component for rendering.
- The rendered result is sent back to the client.
What is a controller in MVC?
Client requests are handled by a controller. The controller performs the following tasks:
- Inspect the validity of incoming requests.
- Perform input validation on any submitted data.
- Invoke components that interact with back-end resources.
- Acquire all the data needed to fulfill the request.
The controller's job is to handle the incoming request and get any data the client is requesting from the server. Any data obtained by the controller gets saved inside the model.
What does the model in MVC do?
The model stores data pertinent to handling the client's request. Any data the client might need to use or see goes in the model.
In stateless applications, data stored in the model only lasts for the current request-response cycle. In stateful applications, the model might persist across multiple invocations.
Once the controller is finished and the model is populated, the next step is to generate a response for the client. That's where the view comes in.
What does the view in MVC do?
The view component in the model-view-controller pattern presents the data stored in the model to the client.
The controller did everything necessary to handle the request. Data obtained during the handling of the request went into the model. In the end, the client wants to see that data.
How is the view implemented?
The view can be implemented in a variety of ways:
- For RESTful web services, the view might simply render JSON.
- For web-based clients, the view might generate an HTML page.
- For desktop apps, the view might build a GUI with JavaFX or Python's Tkinter.
In any case, the component renders a device-compatible view to the client that shows the results of their interaction with the application.
Benefits of the MVC design pattern
The model-view-controller design pattern is simple and effective. The loose coupling and component isolation MVC provides results in many benefits, such as the following:
- The ability to perform parallel development.
- Simplified testing due to isolated dependencies.
- Simplified maintenance and upgrade paths.
The model-view-controller design pattern is pervasive throughout the industry. From JavaScript frameworks like Angular, to Java standards like Spring MVC, an MVC-based approach is a proven strategy for resilient and reliable software development.
Cameron McKenzie has been a Java EE software engineer for 20 years. His current specialties include Agile development; DevOps; Spring; and container-based technologies such as Docker, Swarm and Kubernetes.