As of now, docx4j can create, load and save OpenXML SpreadsheetML packages.
"Why would you use docx4j to do this", I hear you ask, "rather than POI, which focuses on xlsx and binary xls?"
Probably because you like JAXB (as opposed to XML Beans), or you are already using docx4j for docx or pptx, and need to be able to do some stuff with xlsx as well.
Another possible reason is that the jar XML ...