I'm not saying put it in models I'm saying it's part of the Model of MVC. If you've got a class called FooBarService that takes a model and executes business l

I'm not saying put it in models I'm saying it's part of the Model of MVC. If you've got a class called FooBarService that takes a model and executes business logic on it, that FooBarService can still be part of the Model of MVC. If, on the other hand, FooBarService has a handler for a MouseEvent - something that should be done in the Controller - and business logic in it too, now you're violating MVC because your Model and Controller aren't separated. BTW, IMO to name something FooBarService or BazQuxService is a code smell. "Service" carries no significance. Same goes for "Manager" or "Logic" or whatever generic thing you end up using. Any code could be in there. I have to look inside it to see. It also gives you an excuse to make those file huge because anything could be in there. It's a violation of the Single Responsibility Principle. Hah, yes, I'm a Java programmer.