Chapter 11 - Integrating Legacy Code—Wrapping

Summary

What We'll Learn in This Chapter

Why we need to wrap.

What the approaches to wrapping are.

When, and when not, to use the following wrapping technologies: C APIs, dynamic shared libraries, screen scraping, peer-to-peer, and the Common Object Request Broker Architecture (CORBA).

The trade-offs of wrapping.

Information technology shops of today have a huge investment in information technology; unfortunately, the vast majority of it isn't object oriented (OO). In the 1980's it is estimated that over $ 1 trillion was invested in information technology in the United States alone. Needless to say organizations are motivated to retain as much of this investment as possible. Wrapping is a technique in which you make non-OO technology appear to be OO by putting a layer of OO code around it, which is often a critical part of any significant OO project.

A wrapper is a collection of one or more classes that encapsulates access to technology that isn't object-oriented to make it appear as if it is. A wrapper class is any class that is part of a wrapper. Wrapping, as shown in Figure 11.1, is used to provide OO applications access to hardware, operating system features, procedure libraries, function libraries, and even legacy applications. Wrapping allows you to retain your investment in older, non-OO technology by allowing you to reuse it in the new OO applications that you develop.