creating relationship between objects at runtime

I have some object stored as json which have unique key, and based on these keys there is a mapping defined in a spreadsheet.i have implemented one json that has the hieararchy and I read this json in java and store it in some collection. Problem is if hieararchy grows then maintaining this json gets difficult. I wanted to create this hierarchy in java at runtime without creating the static hierarchy in json .Rather i would like to keep jsons of objects separately in db .Please help.