Model View Controller

So far, we have seen lots of concepts, such as the dispatcher servlet, request mapping, controllers, and view resolver; it would be good to see the overall picture of the Spring MVC request flow so that we can understand each component's responsibilities. However, before that, we need to understand the Model View Controller (MVC) concept some more. Every enterprise-level application's presentation layer can logically be divided into the following three major parts:

The following diagram will help you understand the event flow and command flow within an MVC pattern:

Whenever a user interacts with the view by clicking on a link or button, the view issues an event notification to the controller, and the controller issues a command notification to the model to update the data. Similarly, whenever the data in the model gets updated or changed, a change notification event is issued to the view by the model in response, and the view issues a state query command to the model to get the latest data from the model. Here, the model and view can interact directly; this pattern is called the classic MVC pattern. However, what Spring MVC employs is something called a web MVC pattern due to the limitations in the HTTP protocol.

In web MVC, every interaction between the model and view is taken through the controller only. So, the controller acts as a bridge between the model and view. There is no direct interaction between the model and view, as in the classic MVC pattern.