Accessing objects tree structer

karollo · **Joined:** Sun Jun 17, 2007 4:01 pm **Posts:** 5

Hi,
i have a Class Category which has subcategories collection of type Category. Each Category object has also a superCategory reference to it's parent Category object, so it's typical tree structer with many roots possible. All i need to do is to retreive all my Category objects from database as tree structer, not as a list of all Category objects but as a list of root level Category objects and eagerly retreived subcategories, and subcategories of subcategories and so on.

I tried this

Code:

session.createCriteria(Category.class).add(Expression.isNull("superCategory")).setFetchMode("subcategories",FetchMode.EAGER).list();

but is retreives just a plain list of all Category objects, not a tree structer.

Example of my tree structure could be as below:

Category
-Category
--Category
--Category
---Category
---Category
--Category
---Category
Category
-Category
--Category
---Category

The question is: how to retreive all Category objects as a tree structer?

Thanks for any helpful answers

Cameron McKenzie · **Posted:** Mon Aug 10, 2009 7:16 am

Do you have a recursive mapping in your hibernate configuration file for this class? Does the actual mapping reflect this recursive structure?

sbrattla · **Joined:** Wed Dec 10, 2008 5:59 am **Posts:** 47

I worked on something quite similar i little while ago, and i write things down just to remember it. Have a look and see if it can help you a little on your way.

http://blog.brattland.no/?q=node/3

Returning only the root category objects should be as simple as iterating over the results and returning only those objects that do not have a parent.