Hi,

i need some help with managing a persistent tree-structure. mainly it will be used in a user-interface to display hierarchically the stored data

i have allready a solution on the database-side that fits my needs:

tables:
TreeIndex -> an index of my different trees
node, node-relations -> there can be bidirectional n:m relations between the nodes
node-type -> e.g. this node is a country-node and it childs are cities
data-item, data-item-type -> can be attached to a node e.g. the number of inhabitants of a city

now i tried to implement a working services to manage my different trees but its gotten very unhandy and ugly. particularly doing changes to an existing tree seems very troublesome.

anyone knows some reading/books about managing tree-structures with ORM (Hibernate would be great ;) )

What you describe could be way more easily done by two classes (and matching tables):

Country

City

with the 1:n relationship from Countries to cities.

Everything is straight forward.

So why are you trying to do this weired table design?

country and city are only examples.

this tree-structure is needed by at least 3 data-collections (sorry for my bad english ;) ):

- address-data (for at least 2 countries with totaly different structures and today we dont know if tomorrow a structure for a new country like switzerland is needed)
- age
- interest of users

and in the future there might be some more.. so its desirable to keep things generic (or at least to try as hard as i can to do so).

//edit:
in another forum they showed me a way to avoid this n:m rellation. maybe that would make things easier. still it would be nice to have some readings or so :)