UML Weekend Crash Course™ - To Parent Directory

SESSION
29
Design of a Web Application
Session Checklist
✔ Explaining and illustrating the Model 2 Architecture
✔ Explaining and demonstrating how to use Sequence, Collaboration, and
Class diagrams in Web-application design
✔ Explaining the Java technologies that can be applied to Web development
✔ Explaining how to model XML and other markup languages with UML
object hierarchies
In the last session, you partially implemented a Web Model View Controller (MVC) design
by separating out the model into JavaBeans and the view into JSPs. This partial implementation
of the MVC pattern provides significant advantages: independent development,
better cohesion, and easier maintainability. For a full MVC architecture, though, you
need to know how to separate out the controller elements as well.
Model 2 Architecture
The Model 2 Architecture was presented by Sun Microsystems in the early versions of the
servlet specification. It is now a popularly used and discussed Model View Controller
architecture for Java Web applications. The Model 2 Architecture is an MVC architecture
that will separate out the controller elements. This architecture is shown in the UML
Component diagram in Figure 29-1 and the UML Sequence diagram in Figure 29-2. The Model 2
Architecture separates the model (JavaBeans) and the view (JSPs) just as you did in the last
session. In addition, it has a single servlet used as the controller. All HTTP requests for any
part of the Web application will be directed to this controller servlet. The servlet will verify
the input data from the HTTP request and call methods on the JavaBeans to update the data
model. The servlet controller will then forward the request on to a JSP that will render the
view. The JSP will access the JavaBeans to get the data that should appear on the Web page.