I failed with this easy directory/folder example, because I don't know how to write the mapping if first level folders of the directory have the root as parent and all other folders have a folder as parent.

So the data-structure ist the same as you know it from a directory.

There are 2 objects to persist:
- the directory-root, which contains folders (all folders without a parentFolder)
- folders, which can contain other folders

The table Folders looks like this:



If a folder has no parentFolder it is child of the root-object.

This is the mapping for the Collection-Set "childFolders" of a Folder :


But I don't know how to write the mapping for the childFolders of the root?
Because therefor I would have to select all folders which don't have a parentfolder.

Can you please help me?