Collections in MVC architecture

Question

My question concerns the use of collections of entities in a database-access MVC architecture. An example similar to my situation would be a Corporation, which (among other attributes) has a collection of Departments, which (among other attributes) has a collection of Projects, which (among other attributes) has a collection of Employees.
Sometimes, I may want information such as all the Employees in the corporation, which would necessarily involve retrieving all the entities from the database. Other times, I may only want the employees in a certain Department, in which case I wouldn't want to waste the time population all the Department beans with Project and Employee information.
Basically, I'm not sure how to best go about populating Javabeans that contain other Javabeans containing other Javabeans. Obviously, when I go to retrieve a Corporation bean, I don't always want all the Departments, Projects, and Employees. However, it seems like it would be using a lot of redundant code to have one factory that returns just the Department base information (without it's Employees), one factory that returns all the Departments and their Projects (but not the Employees), one factory that returns all the Employees for a given Project (but not ALL the Projects and their Employees), and so on.
I've read plenty of MVC tutorials (and even taken a course in it), but I've never really seen a basic situation such as this addressed. What is the best way to go at this situation? Does anyone know of any tutorials/examples that are similar to this situation?

Answer 1

First let's say your post reminded me my previouse Project where i faced exactly this topic.( not a problem may say ) :)
That's it orr94 ! No MVC related topic, says about these. this may be referenced in your experience of Programming and System Design, with the knowledge of OOP, implementing DBs, Performance issues, and so on...
Simply i can tell you, by my experience, try to feel ( and then find ) what your system is supposed to do? and how it does that?
In a situation when you should give many reports, collecting your information, and the main part is GIVING THE LISTS OF REPORTS, just try to load all of your data. ( here first time spends much time, but after that no time is needed for DB operations. you every time read from your objects ( makin' them Updatable )
But if number of the times you should gather this information, is such small that it dosn't actualy needed to read more than wanted.
So see that there is NO GENERAL ANSWER to this question. ( i found it on that project, spending a month to find any answers. )
YOU SHOULD FIND YOUR ANSWER. try feeling your system by real-time TESTS, that would make you sure about a solution.
P.S. Now as a tip
Create a Database Logic Bean which all related methods go in for CRUD operations on entities, then as friends said, try puttin some flags for reading entities ( e.g in your constructors which use DB bean methods )
and then try different approaches readin the data, see which makes sense to your system.
As the last point, what chintat said ( A Getter() which reads the from db that lists ) is not a good solution, where each call to that getter(), where it'd be many calles, attemps to access db!!! you should read once, then getter() returns a reference ( maybe readonly ) to that list.
I think the question is when to read, where YOU SHOUD FIND THE ANSWER. ;)
nice post, i hope it helps. ;)
Behrad