Programming Jakarta Struts, Second Edition

Why Is Model-View-Controller So Important?

The MVC architectural pattern is not directly related to web applications or Java for that matter. In fact, it’s quite common in Smalltalk applications, which generally have nothing to do with the Web.

As we saw in the previous section, the Model 2 approach is concerned with separating responsibilities in web applications. Allowing a JSP page to handle the responsibilities of receiving the request, executing some business logic, and then determining the next view to display can make for an unattractive JSP page, not to mention the maintenance and extensibility problems this entanglement causes. Application development and maintenance are much easier if the different components of a web application have clear and distinct responsibilities.

The MVC pattern is categorized as a design pattern in many software design books. Although there is much disagreement on the precise definition of the pattern, there are some fundamental ideas.

The MVC pattern has three key components:

Model

Responsible for the business domain state knowledge

View

Responsible for a presentation view of the business domain

Controller

Responsible for controlling the flow and state of the user input

With the MVC pattern, a form of event notification usually takes place to notify the view when some portion of the model changes. However, because a browser in a typical web application has a stateless connection, the notification from the model to the view cannot occur easily.^[2] Of ...