Getting multiple drop down dynamically in JSF - jsf

Question

I have a hierarchy of parent child relationship in database and based on those values, I need to add new values. The hierarchy could be different and the drop down needs to be displayed dynamically. E.g. Lets say we have 2 hierarchies: NorthAmerica>USA>California and NorthAmerica>USA>GWA>Seattle. So when I try to add a new Location, if I select NA at first level, USA at second level and California at third level, then the last drop down should be of the locations which are children of California. In other case, if I select NA at first level, USA at second level, GWA at third level, then fourth drop down should show of Seattle and the last drop down should be of the locations which are children of Seattle.
The number of drop downs are shown based on the values present in the database. I doubt that it can be done using ui:repeat but I am not getting the right direction. It would be great if someone could help with any positive pointers.

Answer 1

If you are able to make Map<K,V> map
Where K=String(Id for value) and V= List<SomeObjectClass>
SomeObjectClass=> String id, String Value.
Now Map will looks like Key
Key Value
1 1.1,1.2
2 2.1,2.2
1.1 1.1.1,1.1.2
1.2 1.2.1,1.2.2
2.1 2.1.1,2.1.2
2.2 2.2.1,2.2.2
So if I use key 1.1 I will get list of 1.1.1, 1.1.2
One more List<ID> this will holds your selected value from drop down. And size will tell you how many drop down need to display.
Put “0” at index 0 in list, list should not be empty. Now loop over List and show number of drop down as size of list.
Dropdown value will be come from map.get(K).
UI:repeat over List<ID> var=varlistId (You know how)
Dropdown: value=#{map.get(VarID)} iteamlevel=” somevariable.level” ItemValue=”somevariable.id” var=”somevariable” DropDown END
UI:repeat END
You need to add selected Id From dropdown to list, and remove if user make any change in previous drop down, and remove all element from List.
Example:
At Page load, you list size will be 1 you have add 0 at 0 index of list, now your UI will show one drop down with map vale where you have two element 1,2;
If you select 1 or 2 from drop down, add this in list at index 1 as add method will add at last.
Now you have to drop down in UI repeat, first drop down will how 1,2 and second drop down will show 2.1,2.2,
Now if you have ten drop down and user change value in 5th drop down, now you need to loop over list and need to remove element from 6th so you list have 6 value and you UI will show only 6 drop down.
Give your suggestion below
Edited:
We can replace the map by some method which will give the next value for drop down. As suggest by #Kukeltje.