1. 复现 ：使用easyexcel导出带下拉框的excel文件，如果下拉框内容过多，下拉框变为了空

2. 解决思路 ： 导出时创建隐藏的sheet，下拉框的取值从隐藏的sheet中获取，下拉框显示正常

3.easyexcel自定义拦截器代码:

import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddressList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;

import javax.servlet.http.HttpServletRequest;
import java.util.List;

/**
 * 自定义拦截器
 *
 * @author feng xing lie
 */
public class CustomSheetWriteHandler implements SheetWriteHandler {

    private static final Logger LOGGER = LoggerFactory.getLogger(CustomSheetWriteHandler.class);

    @Override
    public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {

    }

    @Override
    public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
        LOGGER.info("第{}个Sheet写入成功。", writeSheetHolder.getSheetNo());
        HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
        DataValidationHelper helper = writeSheetHolder.getSheet().getDataValidationHelper();
        // 区间设置 第一列第一行和第二行的数据。
        // 由于第一行是头，所以第一、二行的数据实际上是第二三行
        //从第五行开始 100行都是这个
        //fristRow表示 从第几行开始 到第几行结束  表格行从0开始的
        //firstCol表示 从第几列开始 到第几列结束 表格列从0开始的
        CellRangeAddressList cellRangeAddressList = new CellRangeAddressList(2, 100, 3, 3);
        List<String> classGradeList= (List<String>) request.getSession().getAttribute("classGradeList");
        if(classGradeList==null || classGradeList.size()==0){
            classGradeList.add("目前没有班级");
        }
        String[] classGrades = classGradeList.toArray(new String[classGradeList.size()]);
        /*   解决办法从这里开始   */
        //获取一个workbook
        Workbook workbook = writeWorkbookHolder.getWorkbook();
        //定义sheet的名称
        String hiddenName = "hidden";
        //1.创建一个隐藏的sheet 名称为 hidden
        Sheet hidden = workbook.createSheet(hiddenName);
        //2.循环赋值（为了防止下拉框的行数与隐藏域的行数相对应，将隐藏域加到结束行之后）
        for (int i = 0, length = classGrades.length; i < length; i++) {
            // 3:表示你开始的行数  3表示 你开始的列数
            hidden.createRow( 2+ i).createCell(3).setCellValue(classGrades[i]);
        }
        Name category1Name = workbook.createName();
        category1Name.setNameName(hiddenName);
        //4 A1:A代表隐藏域创建第N列createCell(N)时。以A1列开始A行数据获取下拉数组
        category1Name.setRefersToFormula(hiddenName + "!A1:A" + (classGrades.length + 3));
        //5 将刚才设置的sheet引用到你的下拉列表中
        DataValidationConstraint constraint8 = helper.createFormulaListConstraint(hiddenName);
        DataValidation dataValidation3 = helper.createValidation(constraint8, cellRangeAddressList);
        writeSheetHolder.getSheet().addValidationData(dataValidation3);
    }
}

4. 效果图 ：

5. 原生poi解决办法 ： 参考 这个大佬的文章