Took a look at this one. I don't think we can make them final as we can only generate them after or in configureFieldMetadata.

Ok, right. I saw a constructor initializing them but missed there's an alternative constructor which does it lazily. Not final then, unless you have time to find a way to refactor it all to use constructor initialization only.

That being said, I can see the rationale for the longitude and latitude fields. As for the hash fields, I wonder if it's such a good idea as we probably will need a Map<Integer, String> to store the values.

Good point, I had forgotten that the hash approach has to generate many different fields names. A Map would not be very efficient but we could use an array? The total number of fields being generated is generally quite small, and definitely well known upfront.