When everyone shares a common source for a particular software artifact, upgrading the artifact is simply a matter of placing the new certified copy in that shared location. If everyone has made their own personal copy of that artifact, the work involved in deploying the upgrade is increased dramatically, as is the potential number of people involved. Any time you make a copy of something, even if it is an unaltered copy, that copy will now have to be maintained independently of any other copies that exist.

If you have shared Java components, it is a bad practice to bundle them in your application's .ear file. Place them instead, in a .jar deployed to your application server where your application can share them with other applications.

Similarly, if you have shared JavaScript files, do not bundle them in your .ear file either. Deploy them to your HTTP server where all using applications can access them via URL. To truly share a component, the component needs to be deployed to an area that is accessible to all that could benefit from its use, and everyone who uses the component should obtain it from the same, shared source.

Write once, store once, reuse many times
Cloning programs and systems is such a pervasive technique in our industry that it really would be foolish to suggest that you could do away with the practice completely. There will always be those occasions where it is expedient to grab something that exists and hack it up for your own purposes.

That's just a smart way to get a good start on something.

But to make a habit of mass-producing similar-but-different applications and systems is a bad practice that will ultimately lead to a decline in your overall productivity.

By intentionally designing your software to be reused and deploying reusable software in a common repository, you can still reap the development benefits of cloning without the accompanying negative effects on the lifetime maintenance of your software.

Jeff Chilton (jchilton@teametg.com) is Vice President of Fulfillment at Echo Technology Group, Inc. (at http://www.teametg.com), an IT consulting firm that specializes in enterprise-focused best practices.