Market Perspective: Application Servers
In the span of less than three years, the “application server” has become one
of the hottest commodities in the computer industry. Although the specifi c
defi nition of the term varies widely depending on the source, the general
consensus describes an application server as software or middleware that
facilitates the rapid deployment of e-business applications. (This use of the
term “application server” is different than the popular IT meaning; namely,
a server box that is dedicated to running business applications.) As we will
discuss later, no two application servers are alike; specifi c hardware, operating
system and middleware choices will produce a wide variety of results in such
key areas as performance, scale and security. For now, let’s take a generic
look at the appeal of this class of middleware from the perspective of the
application developer.
Why did the application server become important so fast? Since all
e-business applications share a common need for a base set of system services
(such as persistence, security and transactions), it became readily apparent
that the productivity of e-business application developers would be greatly
improved if these services could be standardized and presented to applications
in a transparent fashion. You will often see such services referred to as
“plumbing” by business programmers, because they are programming activities
that are necessary yet have no direct correlation to business processes. The
connotation is deliberately negative.
The purpose of an application server, therefore, is to hide this plumbing
by transparently extending a set of essential system services to e-business
applications so that business programmers can easily assemble them
from compact pieces of business logic without requiring a deep understanding
of platform-specifi c infrastructure. Business programmers could no longer
afford the time it took to fi gure out how to use system-level services to achieve
business objectives, and application servers were seen as one way to address
this problem.
The primary value proposition of application servers is to facilitate the
development of e-business applications by allowing business programmers
to focus solely on writing business logic; the application server handles all
of the diffi cult system-related chores transparently. This is achieved through
a programming model that partitions the task of developing applications