Hi there,

when upgrading POI-OOXML from an ancient V 3.7 to latest stable 5.2.3, all of a sudden some code caused an IndexOutOfBoundsException when saving the document. Although it is getting thrown in XmlBeans, I guess its more at the XSSF side.

Exception in thread "main" java.lang.IndexOutOfBoundsException
	at org.apache.xmlbeans.impl.store.Xobj.removeElement(Xobj.java:2099)
	at org.apache.xmlbeans.impl.store.Xobj.remove_element(Xobj.java:2130)
	at org.openxmlformats.schemas.spreadsheetml.x2006.main.impl.CTRowImpl.removeC(CTRowImpl.java:146)
	at org.apache.poi.xssf.usermodel.XSSFRow.fixupCTCells(XSSFRow.java:612)
	at org.apache.poi.xssf.usermodel.XSSFRow.onDocumentWrite(XSSFRow.java:582)
	at org.apache.poi.xssf.usermodel.XSSFSheet.write(XSSFSheet.java:3806)
	at org.apache.poi.xssf.usermodel.XSSFSheet.commit(XSSFSheet.java:3749)
	at org.apache.poi.ooxml.POIXMLDocumentPart.onSave(POIXMLDocumentPart.java:467)
	at org.apache.poi.ooxml.POIXMLDocumentPart.onSave(POIXMLDocumentPart.java:472)
	at org.apache.poi.ooxml.POIXMLDocument.write(POIXMLDocument.java:221)
	at CreateExcel.writeToFile(CreateExcel.java:61)
	at CreateExcel.create(CreateExcel.java:23)
	at CreateExcel.main(CreateExcel.java:77)

The problem was that in some function the first row of a sheet was overwritten 1x by mistake but the header cells have been set multiple times in a loop. 

Admitedly this is probably not a common use case, but maybe there could be checked something and a meaninful error could be thrown. Finding the main cause took us some hours because the Exception didn't ring anything :)

below I pasted a small POC which triggers the Exception when the first row is clobbered twice (second run of the function).


Best 
Martin 

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

import org.apache.poi.xssf.usermodel.*;
import org.apache.poi.ss.usermodel.*;

public class CreateExcel {

    private final String o_filename;

    public CreateExcel(String p_filename) {
        o_filename = p_filename;
    }

    public void create() {
    	Workbook wb = new XSSFWorkbook();
        fillData(wb, 1);
        writeToFile(wb);
        System.out.println("First file is ok");
        wb = new XSSFWorkbook();
        fillData(wb, 0);
        writeToFile(wb);

    }


    private void fillData(Workbook p_wb, int startAtRow) {
        Sheet sheet = p_wb.createSheet("sheet123");
Row header =sheet.createRow(0);
boolean headerSet =false;
for (int rownum =startAtRow; rownum< 4; rownum++) {
//	if (!headerSet) {
		fillRow(header,true);
		headerSet =true;
//	}
	
	Row row =sheet.createRow(rownum);
		
	fillRow(row, false);
}
    }

	public void fillRow(Row row, boolean header) {
		String text =header ? "header " : "cell";
		for (int i =0; i < 10; i++) {
			Cell cell =row.createCell(i);
			cell.setCellValue(text +i);
		}
	}


    private void writeToFile(Workbook p_wb) {
        FileOutputStream fileOut = null;
        try {
            fileOut = new FileOutputStream(o_filename);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        try {
            p_wb.write(fileOut);
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            if (fileOut != null) {
                fileOut.close();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public static void main(String[] args) {
        CreateExcel createExcel = new CreateExcel("e://wobo.xlsx");
        createExcel.create();
    }
}