// load XLSX file with an instance of Workbook
Workbook workbook = new Workbook("template.xlsx");
// access CellsCollection of the worksheet containing data to be converted
Cells cells = workbook.getWorksheets().get(0).getCells();
// create & set ExportRangeToJsonOptions for advanced options
ExportRangeToJsonOptions exportOptions = new ExportRangeToJsonOptions();
// create a range of cells containing data to be exported
Range range = cells.createRange(0, 0, cells.getLastCell().getRow() + 1, cells.getLastCell().getColumn() + 1);
// export range as JSON data
String jsonData = JsonUtility.exportRangeToJson(range, exportOptions);
// write data to disc in JSON format
BufferedWriter writer = new BufferedWriter(new FileWriter("output.json"));
writer.write(jsonData);
writer.close();