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Aspects and Middleware

Phillip J. Eby:

But this doesn't make any sense. If your application requires that API to be present, then it's not middleware any more! Middleware, you see, exists in order to wrap applications with additional behavior. If you can't arbitrarily decide whether to stick it in front of an application, it's not middleware any more. It's part of the application.

PJE describes pointless decoupling via WSGI middleware. No argument from me. In the Java world, that a problem is optimally obtained by using AOP for everything. The kinds of things you could could farm out to aspects are much like the ones you can farm out to middleware. Where the variation comes into play is that the set of issues that crosscut an application will vary depending on how you design your application (for example if you use OO domain models, threads and logging will crosscut your application), and on the environment (for example if you are building a webapp or a CMS, character encoding will crosscut your application). I gather this sort of thing is why some people see AOP as a technique of limited application, rather than a programming paradigm - something along the lines of, you don't design a program with AOP, you use it to duck and dive around a program.

February 19, 2007 11:42 PM


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