Report in excel using "apache poi"?

Question

Java

Essence:
When you click on the button, an excel document is downloaded.
It has merged cells that should have their borders painted over
. Problem:
only half of the cell is painted over. The part that was before the merging of two cells

spoiler

HSSFRow row3 = spreadsheet.createRow(rowid++);
 spreadsheet.addMergedRegion(new CellRangeAddress(rowid - 1, rowid, 0, 0));
        cell = row3.createCell(0);
        cell.setCellValue("№");
        cell.setCellStyle(styleCaption);

spoiler

HSSFCellStyle styleCaption = workbook.createCellStyle();
        styleCaption.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        styleCaption.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
        styleCaption.setBorderBottom(HSSFCellStyle.BORDER_THIN);
        styleCaption.setBorderLeft(HSSFCellStyle.BORDER_THIN);
        styleCaption.setBorderRight(HSSFCellStyle.BORDER_THIN);
        styleCaption.setBorderTop(HSSFCellStyle.BORDER_THIN);
        styleCaption.setFillBackgroundColor(HSSFColor.GREY_50_PERCENT.index);
        styleCaption.setFont(font);
        styleCaption.setWrapText(true);
        styleMap.put("styleCaption", styleCaption);

Answer 1

Sergey Gornostaev @TheDeadOne
Get all the regions of the merged cells, when assigning a style to a cell, check if it exists in any of the regions, if it is included in the region, apply the style to all cells of this region.
After merging the cells, you need to manually paint over a non-main cell.