There is very limited support for pivot tables yet in POI, as you've
found. The avenues I can think of for you are:
1. compare before and after XLSX output (it's zipped XML files) to see what
Excel is doing, then replicate that in POI - not typically a simple task.
2. Start with a "template" fil
I'm using POI 3.17 and I've got a basic Pivot table working. Right now,
I have rows, and I'm summing a column.
I'd like to add columns. E.G. one of my source data columns is a period
label. For example, 2018-05 or 2018-07. I'd like each period to be
grouped, and the sums broken out by the Row/
