How to resize a chart using XSSF (Apache POI 3.8)?

Question

I am wondering whether there is a way to resize a chart using Apache POI (XSSF). Currently I am using an Excel template, which has a chart that changes when more data is inserted using namedRanges.

Everything works fine, the only troubles I'm facing are:

• The chart always stays the same size, so if there are more entries, it gets cluttered making the chart kind of useless.
• I am using dates, but I am not able to represent the date as day/month(17/10) on the chart. Basically instead of 04/01/2001, it writes 36982.

The purpose of the workbook is to list several jobs and check whether they took longer on a given date, the graph is for helping to identify the ocurrences of longer elapsed times. The jobs runtime might range from seconds to hours.

This is the code I am using:

package le_package.poi_tests.xssflibrary;

import java.io.*;
import java.text.SimpleDateFormat;
import java.util.Date;

import org.apache.poi.openxml4j.opc.OPCPackage;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Name;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class POIReadFile {
    public static void main(String[] args) {
        try
        {           
            String jobName = "I am a job"; 
            String jobParent = "I am your father, Job.";        
            int rowNum = 40;
            int deface = 4;

            //Open Excel as OOXML
            XSSFWorkbook currentWorkbook = new XSSFWorkbook( OPCPackage.open("include/excelTemplate.xlsx"));

            //Get sheet in position 0
            Sheet currentSheet = currentWorkbook.getSheetAt(0);

            //Get sheet name for processing
            String sheetName = currentSheet.getSheetName();

            //Set values for headers
            currentSheet.getRow(1).getCell(0).setCellValue(jobName);            
            currentSheet.getRow(1).getCell(1).setCellValue(jobParent);              

            for (int i=0; i<rowNum; i++)
            {
                //Create row in a given position
                Row newRow = currentSheet.createRow(i+deface);

                //Create cell within row
                Cell newCell0 = newRow.createCell(0);
                Cell newCell1 = newRow.createCell(1);
                Cell newCell2 = newRow.createCell(2);
                String cellDate = "";

                /* Set CellType
                 *  0 - Numeric | 1 - String | 2 - Formula | 3 - Blank | 4 - Boolean | 5 - Error */
                newCell0.setCellType(0);
                cellDate = "3/"+(i+1)+"/2001 00:00:00";

                //Convert text into date
                Date currentCellDate = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss").parse(cellDate);
                //System.out.println(currentCellDate.toString()+"--"+cellDate);

                //Set CellValue
                newCell0.setCellValue(currentCellDate);


                cellDate = "4/"+(i+1)+"/2001 00:00:00"; 
                currentCellDate = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss").parse(cellDate);
                //System.out.println(currentCellDate.toString()+"--"+cellDate);             
                newCell1.setCellType(0);
                newCell1.setCellValue(currentCellDate);

                //setCellFormula sets the formula to be evaluated by excel, it doesn't need to start with '=' 
                newCell2.setCellFormula("A" + (i+deface+1) + "-B" + (i+deface+1));              
            }           

            //Search for named range
            Name rangeCell = currentWorkbook.getName("startRange");         
            //Set new range for named range 
            String reference = sheetName + "!$A$" + ( deface+1 ) + ":$A$" + ( rowNum+deface );          
            //Assigns range value to named range
            rangeCell.setRefersToFormula(reference);

            rangeCell = currentWorkbook.getName("endRange");            
            reference = sheetName + "!$B$"+(deface+1) + ":$B$" + (rowNum+deface);
            rangeCell.setRefersToFormula(reference);            

            rangeCell = currentWorkbook.getName("elapsedTime");
            reference = sheetName + "!$C$"+(deface+1) + ":$C$" + (rowNum+deface);
            rangeCell.setRefersToFormula(reference);

            //Create a fileStream to write into a file
            FileOutputStream newExcelFile = new FileOutputStream(jobName+".xlsx");

            //Write Stream
            currentWorkbook.write(newExcelFile);

            //Close New Excel File
            newExcelFile.close();           
        }
        catch (Exception e)
        {
            System.out.println("AAAAARGH, I was wounded by the following exception!:");
            e.printStackTrace();
            System.out.println("Sorry, your program is dead :(");
        }
    }
}

Is it possible to do what I need?

Thanks.

*Note: I am not asking to create a chart from the scratch, I only need to resize the one the template has, and change some cells to date instead of the number that is written.

Answer 1

After researching how xlsx works, I was able to find how to get it done.

//Call the partiarch to start drawing
XSSFDrawing drawing = ((XSSFSheet)currentSheet).createDrawingPatriarch();
//Create CTMarket for anchor
CTMarker chartEndCoords = CTMarker.Factory.newInstance();
//The coordinates are set in columns and rows, not pixels.
chartEndCoords.setCol(column);
//Set Column offset
chartEndCoords.setColOff(0);
chartEndCoords.setRow(row);
chartEndCoords.setRowOff(0);
//drawing.getCTDrawing().getTwoCellAnchorArray(0).setFrom(chartStartCoords);
drawing.getCTDrawing().getTwoCellAnchorArray(0).setTo(chartEndCoords);

/*
    This line of code allows to resize the chart:
        The Patriarch is what allows to get control over the drawings, since
        a chart is considered a graph in xlsx you can access it with getCTDrawing.
        Each graph is stored in the tag getTwoCellAnchorArray, where the array position
        is the chart you have; for example getTwoCellAnchorArray(3) would refer to the
        forth graph within the sheet.

        Each getTwoCellAnchorArray has several properties as FROM and TO, which define
        where the existing graph starts and ends.   
*/

If you have any comments, let me know.

Answer 2

1. Give your date cells, date format. Apache poi date format

2. POI cannot modify graphics AFAIK.