J2EE for Enterprise Integration - Guide to Cloud Computing for Business and Technology Managers - page 143

The components of the MVC architecture are as follows:
• View deals with the display on the screens presented to the user.
• Controller deals with the flow and processing of user actions.
• Model deals with the business logic.
MVC architecture modularizes and isolates screen logic, control logic, and
business logic in order to achieve greater flexibility and opportunity for
reuse. A critical isolation point is between the presentation objects and the
application back-end objects that manage the business logic and data. This
enables the user interface to affect major changes on the display screens
without impacting the business logic and data components.
View does not contain the source of data and relies on the model to furnish
the relevant data. When the model updates the data, it notifies as also fur-
nishes the changed data to the view so that it can re-render the display to the
user with the up-to-date data and correct data.
The controller channels information from the view on the user actions
for processing by the business logic in the model. Controller enables an
application design to flexibly handle things such as page navigation and
access to the functionality provided by the application model in case of
form submissions. Thus, controller provides an isolation point between
the model and the view, resulting in a more loosely coupled front end and
back end.
Figure 6.2 gives a complete picture of how objects in the MVC architecture
are mapped to the reference architecture in J2EE.
6.2.4 Overview of J2EE Platform Technologies
These can be subdivided into three main categories, namely, component ser-
vices, horizontal services, and communication services.
6.2.4.1 Component Services
These services assist in expediting and simplifying the development of the
enterprise applications. They insulate the resulting applications from the
underlying J2EE APIs.
6.2.4.1.1 JavaServer Pages (JSP)
As discussed in MVC architecture previously, the objective is to sepa-
rate the presentation and content from the application logic, with the
presentation and content contained in the JSP. JSP is similar to server-
side scripting technology, except that JSP is compiled, whereas scripts are
interpreted. JSP utilizes the Java Servlet technology to achieve server-side
processing.