Learn Java for Web Development

CHAPTER 3: Best Practices in Java EE Web Development 147

Note A good enterprise application consists of multiple tiers, and each tier concentrates on its own

responsibilities/concerns, as explained in Chapters 1 and 2.

Table 3-24. Presentation Tier Java EE Patterns

Presentation Tier Pattern Description

Intercepting Filter Preprocessing and postprocessing of a client web request and response

Front Controller Centralized access point for presentation tier request handling to support

the integration of system services, content retrieval, view management,

and navigation

View Helper Encapsulating business logic so that it is not intertwined with the

presentation logic

Composite View Managing the layout of the view independent of the content

Service to Worker Assembling a microframework of front controller and view helper with a

dispatcher component

Dispatcher View Assembling a microframework of front controller and view helper with a

dispatcher component

Client

Response

Response Filters

Intercepting Filter

Request

Response

Servlet Container

Request

Request Filters

Filter 1 Filter n Servlet

Figure 3-9. Intercepting Filter pattern

In the sections that follow we will look at each of these Java EE web tier patterns.

Intercepting Filter

A web application receives different types of requests that require some kind of processing, for
example, to check whether the client has to be authenticated before proceeding with navigation. The
best technique to provide a processing mechanism for requests is to use a processing component
called a filter. Filters are used when you need to provide request preprocessing or postprocessing
functionalities. The Intercepting Filter pattern comes along with the introduction of filters to the
Servlet specification. This pattern uses one or more filters plugged into the current application to
provide services such as authorization, compression, encryption, and logging. Figure 3-9 illustrates
the Intercepting Filter pattern.