What Bear said. There's a very good reason that Model/View/Controller (MVC) is the prevailing architecture for GUI applications, both web-based and otherwise. It's a LOT easier to maintain an application where the logic and the view are in separate components. It's also a lot easier to port such apps, and you also gain a lot of useful power. For example, one Model can be displayed in multiple views, such as a spreadsheet with matching chart. And conversely, a composite view can source from multiple models.
Also, when you have logic on both View and Model that interacts, it becomes a "treasure hunt" every time you need to find which file something is done in and changes to one object often breaks stuff in the other.
Then there's the practical fact that it's a
son of a
to debug logic on a View Template, such as a JSP. It's punitively difficult to set breakpoints and view/modify data for code in a JSP. Much better to put that stuff in a service class and use the normal debugger features.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.