- Model – The model holds and manipulates domain data (sometimes called business logic or the back end).
- View – A view renders some or all of the data contained within the model.
- Controller – The controller takes input from the user and uses it to update the model and to determine when to redraw the view(s).
MVC is all about separating concerns. The model and views separate the data from the views and the controller and the view separate user input from the views. Another version of the MVC pattern employs the controller as a mediator between the views and model. The controller still takes user input, but now it passes it on to model. It also passes commands from the view to the model and takes events from the model and passes them on to the view. This version provides greater separation as the model and view no longer need to know about each other to communicate.
In this article I am going to describe a real problem I had and demonstrate how I solved it in Java with MVC. I assume familiarity with both Java 6 and Swing. It is very important to implement MVC carefully with a good set of tests.