java poi 导出excel

private void outputExcel(String queryDate, String[] headers,
            List<List<String>> diaochas, HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        HSSFWorkbook workbook = new HSSFWorkbook();
        //createSheet(excel工作表名)
        HSSFSheet sheet = workbook.createSheet(queryDate);
        //下面是设置excel表中标题的样式
        HSSFCellStyle title_style = workbook.createCellStyle();
        title_style.setFillForegroundColor(HSSFColor.SKY_BLUE.index);
        title_style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
        title_style.setBorderBottom(HSSFCellStyle.BORDER_THIN);
        title_style.setBorderLeft(HSSFCellStyle.BORDER_THIN);
        title_style.setBorderRight(HSSFCellStyle.BORDER_THIN);
        title_style.setBorderTop(HSSFCellStyle.BORDER_THIN);
        title_style.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        HSSFFont title_font = workbook.createFont();
        title_font.setColor(HSSFColor.VIOLET.index);
        title_font.setFontHeightInPoints((short) 12);
        title_font.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);
        title_style.setFont(title_font);
        //内容的样式
        HSSFCellStyle content_style = workbook.createCellStyle();
        content_style.setFillForegroundColor(HSSFColor.LIGHT_YELLOW.index);
        content_style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
        content_style.setBorderBottom(HSSFCellStyle.BORDER_THIN);
        content_style.setBorderLeft(HSSFCellStyle.BORDER_THIN);
        content_style.setBorderRight(HSSFCellStyle.BORDER_THIN);
        content_style.setBorderTop(HSSFCellStyle.BORDER_THIN);
        content_style.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        content_style.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
        HSSFFont content_font = workbook.createFont();
        content_font.setBoldweight(HSSFFont.BOLDWEIGHT_NORMAL);
        content_style.setFont(content_font);
        //填充标题内容
        HSSFRow row = sheet.createRow(0);
        for (int i = 0; i < headers.length; i++) {
            //设置标题的宽度自适应
            sheet.setColumnWidth(i, headers[i].getBytes().length * 2 * 256);
            HSSFCell cell = row.createCell(i);
            cell.setCellStyle(title_style);
            HSSFRichTextString text = new HSSFRichTextString(headers[i]);
            cell.setCellValue(text);
        }
        //填充内容 囧。。。偷懒没有建立对象，直接用List存放的数据。
        for (int i = 0; i < diaochas.size(); i++) {
            row = sheet.createRow(i + 1);
            List<String> diaocha = diaochas.get(i);
            for (int j = 0; j < diaocha.size(); j++) {
                HSSFCell cell = row.createCell(j);
                cell.setCellStyle(content_style);
                HSSFRichTextString richString = new HSSFRichTextString(
                        diaocha.get(j));
                cell.setCellValue(richString);
            }
        }
        //这里调用reset()因为我在别的代码中调用了response.getWriter();
        response.reset();
        response.setContentType("application/vnd.ms-excel");
        response.setHeader("Content-disposition", "attachment;filename="
                + queryDate + ".xls");
        OutputStream ouputStream = response.getOutputStream();
        workbook.write(ouputStream);
        ouputStream.flush();
        ouputStream.close();
    }

date_format(formatdate,‘%Y-%m‘)