iTP Secure WebServer System Administrator's Guide (iTPWebSvr 5.1+)

Using NonStop Servlets for JavaServer Pages With
The iTP Secure WebServer
iTP Secure WebServer System Administrator’s Guide—522659-001
9-35
Model-View-Controller Designs
There are two main advantages to this design. There is no processing logic in the
presentation component, it simply retrieves objects or beans created by the controller
and extracts the dynamic content for insertion in the JSP static templates. Thus you will
have a very clear separation of presentation and content, and furthermore as the
controller presents a single point of entry into the application, the management of state
and security are made easier.
These designs are easily implemented using the request dispatcher which allows one
servlet to utilize the services of another servlet. There are two possible scenarios,
including and forwarding. The response of a servlet can include the output of another
servlet. The included servlet can only send output to the client; it cannot alter the header
information. With forwarding, the original servlet cannot send output to the client,
instead it forwards the request and the response to another servlet.
There are three programming steps involved:
1. Obtain a reference to the servlet context by invoking getServletContext( ). The
return value is a javax.servlet.ServletContext object which contains several methods
for the servlet to communicate with the container. The getServletContext ( ) method
is invoked on the ServletConfig object passed in to a servlet’s init( ) method and is
typically stored as a field in the servlet class.
2. Obtain a reference to the request dispatcher object for the servlet in use. Use the
getRequestDispatcher(String name) method which takes in the path and name of the
servlet and returns the request dispatcher object.
3. Invoke either the include or forward method of the RequestDispatcher object. Either
method takes two arguments; the HttpServletRequest and HttpServletResponse
objects.
Figure 9-5. A Model/View/Controller Design
JSP
REQ
RES
CLIENT
BROWSER
WEB CONTAINER
1
2
3
4
Data Storage
Java Bean
or Java Servlet
Servlet
3
4
5
Controller
Model
View
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