I have used SXSSF to output Excel files (xlsx).
When I tried to write RichTextString in SXSSFCell, it was converted to normal text in output file,
(just reflected one cell style to whole cell),
because it seems that SheetDataWriter.java does not support RichTextString.

Then, I tried to change method SheetDataWriter#writeCell according to the rules of OOXML, 
and it worked well in my environment.

Here is my code:
-----------------------------------------
SheetDataWriter.java

public void writeCell(int columnIndex, Cell, cell) throws IOException {
    int celltype = cell.getCellType();
    switch(celltype){
    case Cell.CELL_TYPE_STRING:
        // get RichTextString info
        XSSFRichTextString richText = (XSSFRichTextString) cell.getRichStringCellValue();
        List<CTRElt> listElt = richText.getCTRst().getRList();

        // write cell info to sheet.xml
        String ref = new CellReferec(this._rownum, columnIndex).formatAsString();
        this._output.write("<c r=\"" + ref + "\"");
        CellStyle cellStyle = cell.getCellStyle();
        if(cellStyle.getIndex() != 0) {
            this._output.write(" s=\"" + cellStyle.getIndex() + "\"");
        }  

        this._output.write(" t=\"inlineStr\">");
        this._output.write("<is>");
        
        for(int i = 0; i < listElt.size(); i++) {
            CTRElt elt = listElt.get(i);
            if(elt.isSetRPr()) {
                // the case of having font styles
                this._output.write("<r>");
                this._output.write("<rPr>");
                // write rpr infomation, which CTRElt has (*)
                this._output.write("</rPr>");
                this._output.write("<t");
                if(hasLeadingTrailingSpaces(elt.getT())) {
                    this._output.write(" xml:space=\"preserve\"");
                }
                this._output.write(">");
                outputQuotedString(elt.getT());
                this._output.write("</t>");
                this._output.write("</r>");
            }
        }

        this._output.write("</is>");
        this._output.write("</c>");

    }
}


(Sorry, some parts(*) are ommitted.)
-----------------------------------------

Is there any problems in my code?
If possible, I hope it would be reflected in next version.

Thanks,