EasyExcel

 💡 官方文档已经非常详细

基本用法代码示例（写入自定义列数）

public void export(HttpServletResponse response) {
        ExcelWriter excelWriter = null;
        try {
            // URLEncoder.encode防止中文乱码
            String fileName = URLEncoder.encode(getFileName(), "UTF-8");
            // 设置响应头
            response.setContentType("application/vnd.ms-excel");
            response.setCharacterEncoding("utf-8");
            response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");

            // LongestMatchColumnWidthStyleStrategy 实现自动列宽
            excelWriter = EasyExcelFactory.write(response.getOutputStream())
									.registerWriteHandler(new LongestMatchColumnWidthStyleStrategy())
									.build();

            // 构建表头
            List<List<String>> statHead = buildStatHead();
            // 构建数据
            List<List<Object>> statData = buildStatData();
            // 写Excel
            WriteSheet sheet1 = EasyExcelFactory.writerSheet(sheetNo, sheetName).head(statHead).build();
            excelWriter.write(statData, sheet1);

        } catch (IOException e) {
            log.error("", e);
        } finally {
            if (excelWriter != null) {
                // 关闭流
                excelWriter.finish();
            }
        }
    }

参考资料

EasyExcel官方文档

你要的不固定列excel导入导出，它来啦！