public class YqjgYiZzsjExcelEntity2{ private String rq; private qlzz2 x3ql; private qlzz2 x9qllqyl;}public class qlzz {private String lqyl; private String wsyl; private String zlwd;}我想将YqjgYiZzsjExcelEntity2导出为空excel表，且导出的excel里，x3ql表头下，有lqyl、wsyl、zlwd等子表头，x9qllqyl表头下，也有有lqyl、wsyl、zlwd等子表头，且导出函数为FileUtil.downLoadExcel(fileName,response,workbook);

可以按照以下步骤实现YqjgYiZzsjExcelEntity2导出为空excel表，且导出的excel里，x3ql表头下，有lqyl、wsyl、zlwd等子表头，x9qllqyl表头下，也有有lqyl、wsyl、zlwd等子表头，且导出函数为FileUtil.downLoadExcel(fileName,response,workbook)：

1. 首先，需要创建一个空的Excel模板，包含x3ql和x9qllqyl两个表头以及它们的子表头lqyl、wsyl、zlwd。可以使用ExcelUtil创建一个空的ExcelWriter对象，然后设置表头和子表头。

ExcelWriter writer = ExcelUtil.getWriter();
writer.addHeaderAlias("rq", "日期");
writer.addHeaderAlias("x3ql.lqyl", "x3ql压力");
writer.addHeaderAlias("x3ql.wsyl", "x3ql温度");
writer.addHeaderAlias("x3ql.zlwd", "x3ql质量");
writer.addHeaderAlias("x9qllqyl.lqyl", "x9qllqyl压力");
writer.addHeaderAlias("x9qllqyl.wsyl", "x9qllqyl温度");
writer.addHeaderAlias("x9qllqyl.zlwd", "x9qllqyl质量");

2. 然后，创建YqjgYiZzsjExcelEntity2对象列表，并将其写入ExcelWriter对象中。

List<YqjgYiZzsjExcelEntity2> data = new ArrayList<>();
// 添加空数据
data.add(new YqjgYiZzsjExcelEntity2());
writer.write(data, true);

3. 最后，将ExcelWriter对象转换为Workbook对象，并使用FileUtil.downLoadExcel(fileName,response,workbook)方法进行文件下载。

Workbook workbook = writer.getWorkbook();
FileUtil.downLoadExcel(fileName, response, workbook);