横向合并
Workbook workbook =sheetUtils.exportExcel(dto);
CellRangeAddress craOne = new CellRangeAddress(0, 1, 0, 1);
//CellRangeAddress(第几行开始，第几行结束，第几列开始，第几列结束)
workbook.getSheetAt(0).addMergedRegion(craOne);
支持横向和纵向
纵向合并
PoiMergeCellUtil.mergeCells(workbook.getSheetAt(0), 6, 7);
//sheet页，开始行，需要合并的列数组
//相同内容的列自动合并
