17
Chapt er 1 . COM + Com ponent Services
By now, m ost developers of large- scale enterprise applications are
convinced of the benefits of com ponent - oriented developm ent. They
hav e discovered that by break ing a large system down into sm aller
unit s, they can writ e code t hat is easier to reuse on other projects,
easier t o distribut e across m ult iple com puters, and easier to
m aintain. As long as t hese com ponents adhere to a binary standard
that defines how t hey com m unicate wit h one another, they can be
invoked as needed at runtim e and discarded when they have
finished their work. This type of application is also particularly
suit ed to t he Web, wher e clients request services of rem ote
applications and then, once satisfied, m ove on to other tasks.
For nearly a decade, the Microsoft Com ponent Obj ect Model ( COM)
has been t he standard for com ponent s t hat run on Windows
m achines, including Windows 9x and Me client s and Windows NT
and 2000 servers. The COM m odel is well docum ent ed by the
Microsoft Com ponent Obj ect Model Specification. Tools such as
Visual C+ + and Visual Basic m ake it easy to create COM
com ponent s, and scores of books, t raining classes, and articles are
available to teach program m ers how to use them . Many features of
the Windows operating system are now im plem ent ed as COM
com ponent s, and m any com panies have invested heavily in COM-
based sy stem s of their own.
I n July 2000, Microsoft announced a radically new com ponent m odel
as part of its .NET developm ent platform, suddenly calling into
quest ion the viabilit y of existing COM applications. .NET com ponent s
bear lit tle resem blance t o legacy COM com ponents and are not
backwards com patible. They can be m ade to interoperat e with COM
com ponent s but do not do so naturally.
When it com es to the services and tools program m ers use to build
ent erprise- scale .NET applications, however, one facilit y cont inues
to provide the necessary runtim e infrastructure and services: COM+
com ponent services. These services have been available on
Windows 2000 since it s release, but they will gain greater
im portance in t he m ont hs ahead. As it tur ns out , they offer a bridge
bet ween t radit ional COM and .NET applications, m aking your
understanding and m ast ery of them as import ant now as it has ever
been.
I n this chapter, we provide a quick over view of t he COM+ suite of
com ponent services and t hen introduce you to t he Com ponent
Serv ices Explorer, your prim ary tool for building and m anaging bot h
COM and .NET ent erprise applicat ions. You will also create, debug,
and deploy a sim ple COM+ "Hello Wor ld" application, using a
traditional COM com ponent and learning about COM+ application
types and configured com ponents as you do so.
我的内容管理
展开
