Nifi: Dynamic Attribute Creation

[#1]

I'm trying to come up with a means for dynamic attribute creation. Say I've got a flat Json structured string of name value pairs, in a cassandra db as a text field.

{"A":"1", "B":"2"}

Is there a way to parse this out to a result of an A attribute with value 1 and B attribute with value 2 without explicitly creating a A attribute then polling the jsonpath?

I haven't had any luck in finding a way to dynamically set the lefthand side of an 'update attribute' and wondering if I'm just overlooking something.