Java POI the supplied data appears to be in the Office 2007+ XML
According to the Apache POI Quick Guide, the POIFSFileSystem (or similarly, NPOIFSFileSystem) is only used with .xls (Excel versions through 2003) documents. The equivalent for .xlsx documents (Excel 2007+) is OPCPackage. OPCPackage pkg = OPCPackage.open(new File(“file.xlsx”)); You can create an XSSFWorkbook from the OPCPackage: XSSFWorkbook wb = new XSSFWorkbook(pkg); Or you can just create it … Read more