I would agree that, while I have seen a mega constructor, I'd strongly avoid it. You're correct that having 25 setters may not be a great setup but it is pretty standard. Your bean, assuming that you use
Java been like naming conventions, will be useable in, for example, JSPs in a very easy way.
Also, if your bean implements a little bit of business logic it is far simpler to have the setter methods than a single constructor. One example is if you have a "dirty" flag in your objects. Say you have some collection of Employee classes. Your GUI allows a user to update one or more of these. When the GUI user is done editing maybe they would hit a "Save" button. Now, because you had individual setters you can ask each class if it has been modified. If so you can save it back to the DB.
This is an example when the bean really implements a little bit of business logic behind the scenes.
Basically I'd encourage you to go down the setter route. Yes, it is a pain but it encourages better encapsulation and it just might help
alot in the future.