JAVA实现大数据量导出excel

男娘i 2022-04-02 05:08 454阅读 0赞

JAVA 实现大数据量导出操作时，如果采用POI直接导出，会出现内存溢出的情况。再者EXCEL的SHEET也存在行数的限制，Excel2003版最大行数是655536行、Excel2007版最大行数是1048576行、Excel2010版最大行数是1048576行。

有人说，可以通过分Sheet存放数据啊，可即便分多个sheet也不能解决内容溢出的问题，数据仍然是在一次请求的内存中。

解决方案：

1.      先统计总的记录数，如果大于一定数目则采用压缩文件方式导出

2.      采用分页方式从数据库中获取数据，并生成多个Excel临时文件

3.      将临时文件Excel压缩导出

4.      删除服务器上的临时文件

/**
         * 文件导出
         *
         * @param params
         * @param response
         * @throws Exception
         */
        public void excelDownLoad(Map params, HttpServletResponse response) throws Exception {
            int allRowNumbers = 0;
            int rowMaxCount = 60000;
            //查询记录数
            allRowNumbers = appDao.queryCount("testCommonInfo.infoMangerForAllCount", params);
    
            //是否大数据量（超过6W）
            if (allRowNumbers > rowMaxCount) {
                List list = new ArrayList();
                List downlist = new ArrayList();
                //1.设置相应头
                String filename = "导出TEST.zip";
                filename = new String(filename.getBytes("GBK"), "iso-8859-1");
                response.reset();
                response.setContentType("application/octet-stream;charset=UTF-8");
                response.setHeader("Content-Disposition", "attachment;filename=" + filename);
                response.addHeader("pargam", "no-cache");
                response.addHeader("Cache-Control", "no-cache");
    
                //2.设置批次文件名
                String fileSuff = "";
                SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddHHmmss");
                fileSuff = sdf.format(new Date());
                String fileName = "导出TEST" + fileSuff;
                List<String> fileNames = new ArrayList<String>();  //存放生成的文件名称
                String filePath = "D:/excel/";                   //上线后切换成linux服务器地址
                if (!new File(filePath).exists()) {
                    new File(filePath).mkdirs();
                }
                File zip = new File(filePath + fileName + ".zip");  //压缩文件路径
    
                //3.分批次生成excel
                int tempsize = (allRowNumbers % rowMaxCount) == 0 ? allRowNumbers / rowMaxCount : allRowNumbers / rowMaxCount + 1;
                for (int i = 0; i < tempsize; i++) {
                    if (i == (allRowNumbers / rowMaxCount)) {
                        params.put("startNum", i * rowMaxCount);
                        params.put("endNum", allRowNumbers);
                    } else {
                        params.put("startNum", i * rowMaxCount);
                        params.put("endNum", (i + 1) * rowMaxCount);
                    }
                    list = appDao.queryCount("testCommonInfo.commonInfoForPC", params);
    
                    //3.2生成excel
                    String tempExcelFile = filePath + fileName + "[" + (i + 1) + "].xlsx";
                    fileNames.add(tempExcelFile);
                    FileOutputStream fos = new FileOutputStream(tempExcelFile);
                    int rowMemory = 100;
                    SXSSFWorkbook wb = new SXSSFWorkbook(rowMemory);
                    try {
                        wb = exportDataToExcelXLSX(wb, downlist);
                        wb.write(fos);
                        fos.flush();
                        fos.close();
                    } catch (RuntimeException runMsg) {
                        throw new Exception("查询数据信息异常 ");
                    } finally {
                        fos.flush();
                        fos.close();
                        //手动清除list
                        list.clear();
                        downlist.clear();
                    }
                }
                //4.导出zip压缩文件
                exportZip(response, fileNames, zip);
            } else {
                    ……
            }
        }
    
    
        /**
         * 文件压缩并导出到客户端
         *
         * @param outPut
         * @param fileNames
         * @param zip
         * @throws FileNotFoundException
         * @throws IOException
         */
        private void exportZip(HttpServletResponse response, List<String> fileNames, File zip)
                throws FileNotFoundException, IOException {
            OutputStream outPut = response.getOutputStream();
    
            //1.压缩文件
            File srcFile[] = new File[fileNames.size()];
            for (int i = 0; i < fileNames.size(); i++) {
                srcFile[i] = new File(fileNames.get(i));
            }
            byte[] byt = new byte[1024];
            ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zip));
            out.setEncoding("UTF-8");
            for (int i = 0; i < srcFile.length; i++) {
                FileInputStream in = new FileInputStream(srcFile[i]);
                out.putNextEntry(new ZipEntry(srcFile[i].getName()));
                int length;
                while ((length = in.read(byt)) > 0) {
                    out.write(byt, 0, length);
                }
                out.closeEntry();
                in.close();
            }
            out.close();
    
            //2.删除服务器上的临时文件(excel)
            for (int i = 0; i < srcFile.length; i++) {
                File temFile = srcFile[i];
                if (temFile.exists() && temFile.isFile()) {
                    temFile.delete();
                }
            }
    
            //3.返回客户端压缩文件
            FileInputStream inStream = new FileInputStream(zip);
            byte[] buf = new byte[4096];
            int readLenght;
            while ((readLenght = inStream.read(buf)) != -1) {
                outPut.write(buf, 0, readLenght);
            }
            inStream.close();
            outPut.close();
    
            //4.删除压缩文件
            if (zip.exists() && zip.isFile()) {
                zip.delete();
            }
        }
    
    
        /**
         * 设置excel样式和数值
         *
         * @param wb
         * @param listMap
         * @param companyatr
         * @return
         */
        private static SXSSFWorkbook exportDataToExcelXLSX(SXSSFWorkbook wb, List<Map> listMap) {
            String[] assetHeadTemp = {"系列", "代码", "名称", "凭证号", "状态", "时间", "数量"};
            String[] assetNameTemp = {"TYPE", "CODE", "NAME", "BILLNO", "STATUS", "TIME", "NUM"};
            Sheet sheet = null;
            CellStyle columnHeadStyle = wb.createCellStyle();
            columnHeadStyle.setBorderBottom(HSSFCellStyle.BORDER_THIN);// 下边框
            columnHeadStyle.setBorderLeft(HSSFCellStyle.BORDER_THIN);// 左边框
            columnHeadStyle.setBorderRight(HSSFCellStyle.BORDER_THIN);// 右边框
            columnHeadStyle.setBorderTop(HSSFCellStyle.BORDER_THIN);// 上边框
            columnHeadStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
            columnHeadStyle.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
            columnHeadStyle.setWrapText(true);
            Font f = wb.createFont();// 字体
            f.setFontHeightInPoints((short) 9);// 字号
            f.setBoldweight(HSSFFont.BOLDWEIGHT_BOLD);//BOLDWEIGHT_BOLD);// 加粗
            columnHeadStyle.setFont(f);
            Row row;
            Cell cell;
            sheet = wb.createSheet("sheet");
            row = sheet.createRow(0);
            sheet.createFreezePane(0, 1, 0, 1);
            for (int i = 0; i < assetHeadTemp.length; i++) {
                cell = row.createCell(i);
                cell.setCellStyle(columnHeadStyle);
                cell.setCellValue(assetHeadTemp[i]);
                sheet.setColumnWidth(i, (int) 7000);
            }
            if (listMap != null && listMap.size() > 0) {
                int rowIndex = 1;
                for (Map map : listMap) {
                    row = sheet.createRow(rowIndex++);
                    int index = 0;
                    for (int i = 0; i < assetNameTemp.length; i++) {
                        cell = row.createCell(index++);
                        cell.setCellValue(map.get(assetNameTemp[i]) != null ? map.get(assetNameTemp[i]).toString() : "");
                    }
                }
            }
            return wb;
        }

原文链接：[一路不停][Link 1]

[Link 1]: https://blog.csdn.net/onepersontz/article/details/62054363