Programming Jakarta Struts, 2nd Edition [Electronic resources] نسخه متنی

1.6 What Is a Framework?

I have been using the term
framework
in this chapter without having defined what exactly it is, or how it
adds value in software development. In its simplest form, a framework
is a set of classes and interfaces that cooperate to solve a specific
type of software problem. A framework has the following
characteristics:

• A framework comprises multiple classes or components, each of which
  may provide an abstraction of some particular concept.

• The framework defines how these abstractions work together to solve a
  problem.

• Framework components are reusable.

• A framework organizes patterns at a higher level.

A good framework should provide generic behavior that many different
types of applications can make use of.

There are many interpretations of what constitutes a framework. Some
might consider the classes and interfaces provided by the Java
language a framework, but these are really a library.
There's a subtle, but very important,
difference between a software
library and a framework. A software library contains functions or
routines that your application can invoke. A framework, on the other
hand, provides generic, cooperative components that your application
extends to provide a particular set of functions. The places where
the framework can be extended are known as extension
points. A framework commonly is referred to as an
"upside-down" library because of
the alternate manner in which it operates. Figure 1-5 illustrates the subtle differences between
frameworks and software libraries.

Figure 1-5. A framework and a library are not the same thing

1.6.1 Creation of the Struts Framework

The Struts framework was created by Craig R.
McClanahan and donated to the ASF in 2000. Craig is deeply involved
in the expert groups for the Servlet and JSP specifications and wrote
a large portion of the
Tomcat
implementation. He also speaks at various conferences, including
JavaOne and ApacheCon.

Several committers^[3] have joined the
Struts project, and even more developers have volunteered their time
and effort to improve it and increase its value. As a result, the
framework has gone through several beta releases and a few general
availability (GA) releases, and although many new features have been
added, the framework hasn't strayed far from its
core ideas.

^[3] A committer
is a developer who provides expert direction and advice to steer the
Struts framework on the correct course. A committer has the ability
to modify the source code repository and can cast votes that affect
the future of the framework.

1.6.2 Contribution to the Struts Project

The Struts group always welcomes new participants. To become a
contributor, it's recommended that you first join
the Struts User mailing list. If you like
what you see there, take a look at the Struts Developers mailing
list. This is the best way to get started and become familiar with
the direction of the project. You should read the mailing list
guidelines, at http://jakarta.apache.org/site/maill,
before joining. You can then join one or more of the
Jakarta Project's
mailing lists, including those for Struts, from the URL http://jakarta.apache.org/site/mail2l.

The main project web site for Struts is located at http://jakarta.apache.org/struts/. For more
information on downloading and installing Struts, see Appendix B.