Model/View/Template or Model/View/Controller?
Bill de hÓra has a nice piece on Struts 1 that touches on something about MVC that I’ve never quite liked in the web application context:
In pattern language terms, the MVC pattern has been reapplied to the Web domain without consideration for the forces induced by the Web. MVC frameworks tend to be inwardly focused contraptions of server sided redirects. Alternatives: On the web, a suitable pattern is View, Model, Template. A request to a URL is dispatched to a View. This View calls into the Model, performs manipulations and prepares data for output. The data is passed to a Template that is rendered an emitted as a response. ideally in web frameworks, the controller is hidden from view.
I like the View, Model, Template pattern suggestion, the separation of View (which data can be displayed) and Template (how it gets displayed) is an important one that I think too often gets lost in web application development.
If only the framework could be the entire controller all on its own though! Even the Ruby On Rails (the poster boy web application framework of the moment) cannot do everything unaided. Writing controllers is not too bad if you are exposing RESTful resources – much custom controller logic is then reusable though things like authentication still intrude. RPC oriented web appications are the ones that can really end up suffering from horrendously complex controller definitions.
The other main difference between Java/Struts1 and something like RoR is the considerable benefit gained by being able to define the controller completely within in the host language rather then having to resort to a code+XML definition. I don’t think this should be underestimated. Personally I have always found the biggest impediment to grokking, testing and maintaining Java/Struts1 application code was the mixed Java/XML implementation, and the IDE support it almost demands when used in anger.
BTW, big contratulations to Bill on getting the APP spec (nearly) finished!
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