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the client tier, which takes care of rendering the user interfaces. The application servers
in n-tier architecture host remotely accessible business components. These are accessed
by the presentation layer web server over the network using native protocols. Figure 1-4
shows the n-tier application.
Figure 1-4. N-tier application
Java EE Architecture
Developing n-tier distributed applications is a complex and challenging job. Distributing
the processing into separate tiers leads to better resource utilization. It also allows alloca-
tion of tasks to experts who are best suited to work and develop a particular tier. The web
page designers, for example, are more equipped to work with the presentation layer on
the web server. The database developers, on the other hand, can concentrate on develop-
ing stored procedures and functions. However, keeping these tiers as isolated silos serves
no useful purpose. They must be integrated to achieve a bigger enterprise goal. It is
imperative that this is done leveraging the most efficient protocol; otherwise, this leads to
serious performance degradation.
Besides integration, a distributed application requires various services. It must be
able to create, participate, or manage transactions while interacting with disparate infor-
mation systems. This is an absolute must to ensure the concurrency of enterprise data.
Since n-tier applications are accessed over the Internet, it is imperative that they are
backed by strong security services to prevent malicious access.
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