Create Java Apache POI Line Chart where Dates appear on the horizontal X-axis

I’m trying to create a simple line chart using the Java Apache POI which is essentially a time series, consisting of a Date and a numeric value:

2019-01-01,100.0
2019-01-02,99.0
2019-01-03,98.5
...

I would like for the dates to appear on the x-axis. However, this seems to be difficult to achieve. I can do it manually in Excel but not via the API.

Answer

This is actually very easy using the current apache poi 4.1.0 ;-).

There is an example for creating line charts in https://svn.apache.org/repos/asf/poi/trunk/src/examples/src/org/apache/poi/xssf/usermodel/examples/. This one can take as basis.

The only things you need to know additional is that dates are stored as numeric values in double precision. So the category axis values come fromNumericCellRange and not fromStringCellRange. And if really a date axis is needed instead of a category axis, XDDFDateAxis must be created instead of XDDFCategoryAxis.

But.

Additional problems result from Microsofts weird decisions to make things default in Excel versions later than 2007. In Excel versions later than 2007 category axes are no more text axes type by default. Even date axes are no more date axes type by default. Instead they are “auto” type dependent on the data. So we need explicitly set that we do not want that auto type. Also axes number formats are no more linked to the source. So we need set even that explicitly.

Complete example:

import java.io.FileOutputStream;
import org.apache.poi.xssf.usermodel.*;
import org.apache.poi.ss.usermodel.DataFormat;
import org.apache.poi.xddf.usermodel.*;
import org.apache.poi.xddf.usermodel.chart.*;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.ss.util.CellReference;

import java.util.GregorianCalendar;

class CreateExcelLineChartDataAxis {

 private static void addLineChart(XSSFSheet sheet, CellRangeAddress anchorRange, 
  CellRangeAddress[] titleRanges, CellRangeAddress[] dataRanges, PresetColor[] lineColors) {

  XSSFDrawing drawing = sheet.createDrawingPatriarch();
  XSSFClientAnchor anchor = drawing.createAnchor(0, 0, 0, 0, 
   anchorRange.getFirstColumn(), 
   anchorRange.getFirstRow(),
   anchorRange.getLastColumn(),
   anchorRange.getLastRow()
  );
  XSSFChart chart = drawing.createChart(anchor);

  chart.displayBlanksAs(DisplayBlanks.GAP);

  XDDFChartLegend legend = chart.getOrAddLegend();
  legend.setPosition(LegendPosition.BOTTOM);

  XDDFCategoryAxis bottomAxis = chart.createCategoryAxis(AxisPosition.BOTTOM);
  // if a date axis is needed instead of a category axis, comment the above and uncomment the next
  //XDDFDateAxis bottomAxis = chart.createDateAxis(AxisPosition.BOTTOM);

  XDDFValueAxis leftAxis = chart.createValueAxis(AxisPosition.LEFT);
  leftAxis.setCrosses(AxisCrosses.AUTO_ZERO);
  leftAxis.setCrossBetween(AxisCrossBetween.BETWEEN);
  XDDFChartData data = chart.createData(ChartTypes.LINE, bottomAxis, leftAxis);
  data.setVaryColors(false);
  //XDDFDataSource<String> cat = XDDFDataSourcesFactory.fromStringCellRange(sheet, dataRanges[0]);
  // we have dates (numeric data) as category values
  XDDFDataSource<Double> cat = XDDFDataSourcesFactory.fromNumericCellRange(sheet, dataRanges[0]);
  for (int s = 1; s < dataRanges.length; s++) {
   XDDFNumericalDataSource<Double> ser = XDDFDataSourcesFactory.fromNumericCellRange(sheet, dataRanges[s]);
   XDDFChartData.Series series = data.addSeries(cat, ser);
   series.setTitle(
    sheet.getRow(titleRanges[s].getFirstRow()).getCell(titleRanges[s].getFirstColumn()).getStringCellValue(), 
    new CellReference(sheet.getSheetName(), titleRanges[s].getFirstRow(), titleRanges[s].getFirstColumn(), true, true)
   );
   if (series instanceof XDDFLineChartData.Series) {
    ((XDDFLineChartData.Series)series).setSmooth(false);
   }
  }
  chart.plot(data);

  // some corrections
  // set line colors (necessary for LibreOffice or OpenOffice Calc to show the lines)
  for (int s = 0; s < data.getSeriesCount(); s++) {
   solidLineSeries(data, s, lineColors[s]);
  }

  // some proper default options for Excel versions later than 2007
  if (chart.getCTChart().getPlotArea().getCatAxList().size() > 0) {
   if (chart.getCTChart().getPlotArea().getCatAxArray(0).getAuto() == null) {
    chart.getCTChart().getPlotArea().getCatAxArray(0).addNewAuto().setVal(false); // no auto axis type
   } else {
    chart.getCTChart().getPlotArea().getCatAxArray(0).getAuto().setVal(false); // no auto axis type
   }
   if (chart.getCTChart().getPlotArea().getCatAxArray(0).getNumFmt() == null) {
    chart.getCTChart().getPlotArea().getCatAxArray(0).addNewNumFmt().setSourceLinked(true); // number format linked to source
   } else {
    chart.getCTChart().getPlotArea().getCatAxArray(0).getNumFmt().setSourceLinked(true); // number format linked to source  
   }
   chart.getCTChart().getPlotArea().getCatAxArray(0).getNumFmt().setFormatCode(""); // dummy
  } else if (chart.getCTChart().getPlotArea().getDateAxList().size() > 0) {
   if (chart.getCTChart().getPlotArea().getDateAxArray(0).getAuto() == null) {
    chart.getCTChart().getPlotArea().getDateAxArray(0).addNewAuto().setVal(false); // no auto axis type
   } else {
    chart.getCTChart().getPlotArea().getDateAxArray(0).getAuto().setVal(false); // no auto axis type
   }
   if (chart.getCTChart().getPlotArea().getDateAxArray(0).getNumFmt() == null) {
    chart.getCTChart().getPlotArea().getDateAxArray(0).addNewNumFmt().setSourceLinked(true); // number format linked to source
   } else {
    chart.getCTChart().getPlotArea().getDateAxArray(0).getNumFmt().setSourceLinked(true); // number format linked to source  
   }
   chart.getCTChart().getPlotArea().getDateAxArray(0).getNumFmt().setFormatCode(""); // dummy
  }
 }

 private static void solidLineSeries(XDDFChartData data, int index, PresetColor color) {
  XDDFSolidFillProperties fill = new XDDFSolidFillProperties(XDDFColor.from(color));
  XDDFLineProperties line = new XDDFLineProperties();
  line.setFillProperties(fill);
  XDDFChartData.Series series = data.getSeries(index);
  XDDFShapeProperties properties = series.getShapeProperties();
  if (properties == null) {
   properties = new XDDFShapeProperties();
  }
  properties.setLineProperties(line);
  series.setShapeProperties(properties);
 }

 public static void main(String[] args) throws Exception {

  Object[][] data = new Object[][] {
   new Object[] {"Date", "Value"},
   new Object[] {new GregorianCalendar(2019,0,1), 100d},
   new Object[] {new GregorianCalendar(2019,0,2), 99d},
   new Object[] {new GregorianCalendar(2019,0,3), 98d},
   new Object[] {new GregorianCalendar(2019,2,15), 99.5},
   new Object[] {new GregorianCalendar(2019,3,15), null},
   new Object[] {new GregorianCalendar(2019,4,15), 10d},
   new Object[] {new GregorianCalendar(2019,5,15), 50d}
  };

  try (XSSFWorkbook workbook = new XSSFWorkbook();
       FileOutputStream fileout = new FileOutputStream("Excel.xlsx") ) {

   DataFormat format = workbook.createDataFormat();
   XSSFCellStyle dateStyle = workbook.createCellStyle();
   dateStyle.setDataFormat(format.getFormat("yyyy-MM-dd"));

   XSSFSheet sheet = workbook.createSheet();
   XSSFRow row;
   int rowNum = 0;
   for (Object[] rowData : data) {
    row = sheet.createRow(rowNum++);
    for (int c = 0; c < rowData.length; c++) {
     if (rowData[c] instanceof String) {
      row.createCell(c).setCellValue((String)rowData[c]);
     } else if (rowData[c] instanceof GregorianCalendar) {
      row.createCell(c).setCellValue((GregorianCalendar)rowData[c]);
      row.getCell(c).setCellStyle(dateStyle);
     } else if (rowData[c] instanceof Double) {
      row.createCell(c).setCellValue((Double)rowData[c]);
     } else {
      row.createCell(c);
     }
    }
   }

   sheet.setColumnWidth(0, 12*256);

   addLineChart(sheet, new CellRangeAddress(0, 15, 3, 14), // chart in range D1:O16
    new CellRangeAddress[]{
     new CellRangeAddress(0, 0, 0, 0), // title for x (cat)
     new CellRangeAddress(0, 0, 1, 1) // title for series 1
    },
    new CellRangeAddress[]{
     new CellRangeAddress(1, data.length-1, 0, 0), // data x (cat)
     new CellRangeAddress(1, data.length-1, 1, 1) // data series 1
    },
    new PresetColor[] {PresetColor.BLUE}
   );

   workbook.write(fileout);
  }

 }
}