使用EasyExcel实现excel导出，支持百万大数据量导出-----超简单_easyexcel导出大量数据(1)

记、源码讲义、实战项目、大纲路线、讲解视频，并且后续会持续更新**//每次查询20w数据，每次写入20w数据。//一个sheet装100w数据。

玉泽写

1094人浏览 · 2024-04-28 14:13:56

玉泽写 · 2024-04-28 14:13:56 发布


3.核心导出代码

public void exportSurfList2(StatisticsRequestVo requestVo,HttpServletResponse response) throws IOException {
log.info(“地面统计查询列表导出开始！*****”);
//文件名
String fileName =String.valueOf(System.currentTimeMillis());

    OutputStream outputStream =null;
    try {
        //记录总数:实际中需要根据查询条件进行统计即可:一共多少条
        int totalCount=mapper.seleCount();
        //每一个Sheet存放100w条数据
        Integer sheetDataRows = ExcelConstants.PER_SHEET_ROW_COUNT;
        //每次写入的数据量20w,每页查询20W
        Integer writeDataRows = ExcelConstants.PER_WRITE_ROW_COUNT;
        //计算需要的Sheet数量
        Integer sheetNum = totalCount % sheetDataRows == 0 ? (totalCount / sheetDataRows) : (totalCount / sheetDataRows + 1);
        //计算一般情况下每一个Sheet需要写入的次数(一般情况不包含最后一个sheet,因为最后一个sheet不确定会写入多少条数据)
        Integer oneSheetWriteCount = sheetDataRows / writeDataRows;
        //计算最后一个sheet需要写入的次数
        Integer lastSheetWriteCount = totalCount % sheetDataRows == 0 ? oneSheetWriteCount : (totalCount % sheetDataRows % writeDataRows == 0 ? (totalCount / sheetDataRows / writeDataRows) : ((totalCount % sheetDataRows)+ / writeDataRows + 1));
        outputStream = response.getOutputStream();
        //必须放到循环外，否则会刷新流
        ExcelWriter excelWriter = EasyExcel.write(outputStream).build();
        //开始分批查询分次写入
        for (int i = 0; i < sheetNum; i++) {
            //创建Sheet
            WriteSheet sheet = new WriteSheet();
            sheet.setSheetName("Sheet"+i);
            sheet.setSheetNo(i);
            //循环写入次数: j的自增条件是当不是最后一个Sheet的时候写入次数为正常的每个Sheet写入的次数,如果是最后一个就需要使用计算的次数lastSheetWriteCount
            for (int j = 0; j < (i != sheetNum - 1 ? oneSheetWriteCount : lastSheetWriteCount); j++) {
                //分页查询一次20w
                Page page1 = new Page(j + 1 + oneSheetWriteCount * i, writeDataRows);
                //查询分页列表---按照自己的业务查列表，分页这个一定要使用这个：page1.getPageNum(),page1.getPageSize()！！！
                List<Map<String, Object>> list = mapper.selectList(page1.getPageNum(),page1.getPageSize());
                List<AltitudeMonExportExcelVO > SurfDayList = new ArrayList<>();
               //写入到excel:
                /**************z只需要选择一种方式即可*****************/
                //这里可以通过设置includeColumnFiledNames、excludeColumnFiledNames导出什么字段，可以动态配置，前端传过来那些列，就导出那些列
                //方式1、只导出v01301这一列
                Set<String> includeColumnFiledNames = new HashSet<String>();
                includeColumnFiledNames.add("v01301");
                WriteSheet writeSheet = EasyExcel.writerSheet(i, "Sheet" + (i + 1)).head(AltitudeMonExportExcelVO.class).includeColumnFiledNames(includeColumnFiledNames)
                        .registerWriteHandler(new LongestMatchColumnWidthStyleStrategy()).build();
                //方式2、排除v01301这一列，其他的全部导出
                Set<String> excludeColumnFiledNames = new HashSet<String>();
                excludeColumnFiledNames.add("v01301");
                WriteSheet writeSheet = EasyExcel.writerSheet(i, "Sheet" + (i + 1)).head(AltitudeMonExportExcelVO.class).excludeColumnFiledNames(includeColumnFiledNames)
                        .registerWriteHandler(new LongestMatchColumnWidthStyleStrategy()).build();
                excelWriter.write(list, writeSheet);
                //方式3、不做设置，全部导出
                WriteSheet writeSheet = EasyExcel.writerSheet(i, "Sheet" + (i + 1)).head(AltitudeMonExportExcelVO.class)
                        .registerWriteHandler(new LongestMatchColumnWidthStyleStrategy()).build();
                excelWriter.write(list, writeSheet);
            }
        }
        // 下载EXCEL，返回给前段stream流
        response.setContentType("application/octet-stream");
        response.setCharacterEncoding("utf-8");
        response.setHeader("Content-disposition", "attachment;filename*=utf-8''" + fileName + ".xlsx");
        excelWriter.finish();
        outputStream.flush();
        outputStream.close();
        log.info("*********地面统计查询列表导出结束！**************");
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        if (outputStream != null) {
            outputStream.close();
        }
    }

}


4.配置类

public class ExcelConstants {
//一个sheet装100w数据
public static final Integer PER_SHEET_ROW_COUNT = 1000000;
//每次查询20w数据，每次写入20w数据
public static final Integer PER_WRITE_ROW_COUNT = 200000;