Whether it is Microsoft Transaction Server, COM+, BEA Weblogic or IBM WebSphere, all application servers provide developers with features to make their lives easier, and to make middleware scalable. Database connection pooling, object caching and application fault tolerance are but a few of the benefits of the best application servers.

Each application server has its own development considerations, requirements and quirks, though. COM+ can only house Microsoft-based objects; the J2EE servers can only house Java (or perhaps COM objects, with COM/Java bridges). Furthermore, each J2EE application server has its own management tools, configuration system and optimizations. The price of application servers varies wildly, also: COM+ is free with Windows 2000 Server; BEA installations can run into the hundreds of thousands of dollars.

Consequently, the choice of middleware is one of the fundamental decisions for a company.

Personally, I prefer the Microsoft application server (MTS in NT 4.0, COM+ in Windows 2000), primarily for its low cost. Objects can be written in Visual Basic, Visual C++, Visual J++, or any of the other languages that support COM objects.