I try to create a pivot chart from from a pivot table with apache poi. I am able to create a chart from a fixed area in the sheet, where the pivot table should be. But i need to be able to determine the area from the pivot table.

This function creates a pivot chart from a pivot table, where the range is hard coded and this works so far:

public void createPivotChart(XSSFWorkbook workbook, XSSFPivotTable pivotTable, String pivotSheetName, ReportConfigDTO config) {


        XSSFSheet chartSheet = workbook.createSheet(pivotSheetName);
        //set default style for cells -> erste spalte
        chartSheet.setDefaultColumnStyle(0, cellStyle);

        List<ReportConfigDTO.Chart> chartsFields = config.getReportDefinition().getCharts();

        int startCol = 0;

        for (ReportConfigDTO.Chart chartFields : chartsFields) {
            XSSFDrawing drawing = chartSheet.createDrawingPatriarch();
            XSSFClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, startCol, 1, 10, 25);

            XSSFChart chart = drawing.createChart(anchor);

            PivotChartLegendPositionENUM legendPosition = PivotChartLegendPositionENUM.fromString(chartFields.getLegendPosition());
            XDDFChartLegend legend = chart.getOrAddLegend();
            legend.setPosition(LegendPosition.valueOf(legendPosition.toString()));

            XDDFCategoryAxis bottomAxis = chart.createCategoryAxis(AxisPosition.BOTTOM);
            XDDFValueAxis leftAxis = chart.createValueAxis(AxisPosition.LEFT);
            leftAxis.setCrosses(AxisCrosses.AUTO_ZERO);
            leftAxis.setCrossBetween(AxisCrossBetween.BETWEEN);

            XSSFSheet pivotSheet = (XSSFSheet) pivotTable.getParent();


            //the cell range needs to be determined dynamically and should not be hard coded
            XDDFDataSource<String> categories = XDDFDataSourcesFactory.fromStringCellRange(
                    pivotSheet, new CellRangeAddress(9, 15, 0, 0));
            XDDFNumericalDataSource<Double> values = XDDFDataSourcesFactory.fromNumericCellRange(
                    pivotSheet, new CellRangeAddress(9, 15, 1, 1));

            XDDFChartData data = chart.createData(ChartTypes.BAR, bottomAxis, leftAxis);


            Series series = data.addSeries(categories, values);


            series.setTitle("Charttitle", null); 


           if (data instanceof XDDFBarChartData) {
                ((XDDFBarChartData) data).setBarDirection(BarDirection.COL);
                ((XDDFBarChartData) data).setBarGrouping(BarGrouping.STACKED);
            }

            chart.plot(data);

    }

How can i determine the area of the pivot table in the sheet to create the CellRangeAddress?

I tried to determine the cell reference with:

new CellReference(pivotTable.getCTPivotTableDefinition().getLocation().getRef()

but this gives me some incorrect area. (mostly [A3:B4]).
I also tried to loop through the sheet, but the sheet seems to be empty, but the creation of the chart works so far, so it can not be empty:

chartSheet.getLastRowNum() //returns -1

I read that Apache POI does not know how much space a pivot table representation takes in the sheet. is that true? Can it be determined somehow or is there another way to create the chart based on a pivot table of unknown size?