UML Weekend Crash Course™ - To Parent Directory

298
Sunday Afternoon
Model
Controller
JavaBeans
Web
Browser
Java
Servlet
View
JSP pages
with HTML
content
Figure 29-1
UML Component diagram, Model 2 Architecture
Web Browser
Servlet
Controller
JSP pages JavaBeans Database
send HTTP request for servlet
verify HTTP request parameters
fulfill business logic of the request
update/query database
forward HTTP request to the
appropriate view
get data from JavaBeans
generate output
send HTTP response
Figure 29-2 UML Sequence diagram, Model 2 Architecture
The controller servlet of the Model 2 Architecture offers some additional benefits beyond
the high cohesion and good maintainability of MVC. Because all requests for the Web application
come through one servlet, the developer can place generic security checks and audit
logging code in the servlet and that code will be run for any request for any part of the Web
application.
In the discussion of the case study in Session 28, the two JSP views were separated from
the model. For a full Model 2 Architecture, the development team now adds a single servlet
that will receive all requests that are sent by the Web browser for any part of the Web
application. In this case, the development team decides that having separate controllers for
the wired Web clients and wireless Web clients could enhance maintainability. Thus, they
use two servlet controllers instead of the usual one. Their new architecture is shown in
Figure 29-3.