Java Reference
In-Depth Information
This component is responsible for allowing secured access to the presentation tier
Java Server Pages ( JSP) provides the view components of the OMS application.
Dispatcher Servlet
The dispatcher servlet intercepts all the incoming requests that cross the security layer.
It invokes the appropriate page controller for each user action. It is also responsible for
picking up the appropriate view component and merging it with the model to prepare
the final response.
Page Controller
A page controller is invoked by the dispatcher servlet for each action triggered by the
user. The page controller in turn interacts with the business tier components. It takes the
model returned by the business tier and a logical reference to the next view and passes
them to the dispatcher servlet.
Proxy Factory Bean and Business Interfaces
The proxy factory bean and the business interfaces are used to generate proxy objects to
access the business tier components. The proxy objects hide the networking details for
accessing remote business objects. The business interfaces are used by page controllers
to invoke methods on the business object proxy. The business interfaces play a role simi-
lar to EJB home interfaces.
Business Tier
The business tier is responsible for executing the business rules. Distributing the busi-
ness logic components is one important decision that can be made up front. This will
help you choose the appropriate remoting technology. For the example OMS, the cus-
tomer wants to expose the business logic only to external retail outlets over some form of
HTTP remoting. Also, the team is not conversant with EJB. Hence, I have decided to use
the fast, lightweight Hessian remoting, which is based on HTTP. It can be used to export
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