Your ActionForm for your HTML form, POJO as your model
In my previous company I have developed an online recruitment system in Struts framework. Have I ever mentioned why I prefer working in a team? It's because it's easier for other to point out your mistake. And because I am a self-taught, self-proclaimed Struts user and a lone developer during that time, it wasn't very easy to know what I was doing wrong.
So what did I do wrong?
Eventhough the app was working completely fine, I made my model classes extend ActionForm. I just found out that this is very very very bad! ActionForm classes should only have to do with your HTML form(To get data from a form and to validate) and not your model classes. You model classes, as much as possible, should be POJOs. But well, the app did work. I'll be sure to remember this the next time I use struts.
This realization came to me when I examined the code in Head First Servlets and JSP's Struts Beer App when I finally decided to read the book(seriously) after 2 years. Lolz!