需求背景：有一个需求要做下拉框的值有100多条，同时这个excel是一个多sheet的导入模板
直接用easyexcel 导出，会出现下拉框的值过多，导致生成出来的excel模板无法正常展示下拉功能
使用的easyexcel版本：
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>easyexcel</artifactId>
<version>2.2.6</version>
</dependency>
自定义处理器
package com.manager.utils;
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 java.util.Map;
/**
* 解决使用 easyExcel导出模板，下拉框数据超长，导出模板后，下拉框数据不展示问题
* @author yjj
* @date 2025/02/18 10:16
**/
public class EasyExcelCellWriteHandler implements SheetWriteHandler {
public static final String SHEET_NAME = "下拉框隐藏表hidden";
/**
* 设置阈值，避免生成的导入模板下拉值获取不到
*/
private static final Integer LIMIT_NUMBER = 50;
private Map<Integer, String[]> map = null;
public EasyExcelCellWriteHandler(Map<Integer, String[]> map) {
this.map = map;
}
@Override
public void beforeSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
}
@Override
public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
// 这里可以对cell进行任何操作
Sheet sheet = writeSheetHolder.getSheet();
DataValidationHelper helper = sheet.getDataValidationHelper();
Class<?> headClass = writeSheetHolder.getClazz();
// k 为存在下拉数据集的单元格下表 v为下拉数据集
map.forEach((k, v) -> {
System.out.println("Key = " + k + ", Value = " + v);
// 设置下拉单元格的首行 末行 首列 末列
CellRangeAddressList rangeList = new CellRangeAddressList(EasyExcelUtils.headRowNumber(headClass), 65536,k,k);
// 如果下拉值总数大于50，则使用一个新sheet存储，避免生成的导入模板下拉值获取不到
if (v.length > LIMIT_NUMBER) {
//定义sheet的名称
//1.创建一个隐藏的sheet 名称为 hidden + k
String sheetName = SHEET_NAME +sheet.getSheetName() + k;
Workbook workbook = writeWorkbookHolder.getWorkbook();
Sheet hiddenSheet = workbook.createSheet(sheetName);
for (int i = 0, length = v.length; i < length; i++) {
// 开始的行数i，列数k
hiddenSheet.createRow(i).createCell(k).setCellValue(v[i]);
}
Name category1Name = workbook.createName();
category1Name.setNameName(sheetName);
String excelLine = getExcelLine(k);
// =hidden!$H:$1:$H$50 sheet为hidden的 H1列开始H50行数据获取下拉数组
String refers = "=" + sheetName + "!$" + excelLine + "$1:$" + excelLine + "$" + (v.length + 1);
// 将刚才设置的sheet引用到你的下拉列表中
DataValidationConstraint constraint = helper.createFormulaListConstraint(refers);
DataValidation dataValidation = helper.createValidation(constraint, rangeList);
writeSheetHolder.getSheet().addValidationData(dataValidation);
// 设置存储下拉列值得sheet为隐藏
int hiddenIndex = workbook.getSheetIndex(sheetName);
if (!workbook.isSheetHidden(hiddenIndex)) {
workbook.setSheetHidden(hiddenIndex, true);
}
}
// 下拉列表约束数据
DataValidationConstraint constraint = helper.createExplicitListConstraint(v);
// 设置约束
DataValidation validation = helper.createValidation(constraint, rangeList);
// 阻止输入非下拉选项的值
validation.setErrorStyle(DataValidation.ErrorStyle.STOP);
validation.setShowErrorBox(true);
validation.setSuppressDropDownArrow(true);
validation.createErrorBox("提示", "此值与单元格定义格式不一致");
// validation.createPromptBox("填写说明：","填写内容只能为下拉数据集中的单位，其他单位将会导致无法入仓");
sheet.addValidationData(validation);
});
}
/**
* 返回excel列标A-Z-AA-ZZ
*
* @param num 列数
* @return java.lang.String
*/
private String getExcelLine(int num) {
String line = "";
int first = num / 26;
int second = num % 26;
if (first > 0) {
line = (char) ('A' + first - 1) + "";
}
line += (char) ('A' + second) + "";
return line;
}
}
导出工具类
/**
* 支持超长下拉框展示
* 下载导入模板 - 支持多sheet
*/
public static void writeTemplateBoxTooLong(HttpServletResponse response, ExcelModel excelModel) {
ExcelWriter excelWriter = null;
try {
excelWriter = EasyExcel.write(outputStream(excelModel.getFileName(), response))
.registerConverter(new DateConverter())
.useDefaultStyle(false)
.build();
List<ExcelModel.Sheet<?>> sheets = excelModel.getSheets();
for (int i = 0; i < sheets.size(); i++) {
ExcelModel.Sheet<?> sheet = sheets.get(i);
WriteSheet writeSheet;
if (ExtraOption.class.isAssignableFrom(sheet.getHeadClass())) {
writeSheet = EasyExcel.writerSheet(i, sheet.getSheetName())
.registerWriteHandler(new LongestMatchColumnWidthStyleStrategy())
.registerWriteHandler(HorizontalCellStyleStrategyFactory.optStyleStrategy())
.head(sheet.getHeadClass())
.sheetName(sheet.getSheetName())
.build();
} else {
Map<Integer, String[]> map = buildExcelDropDownSetField(sheet.getHeadClass());
writeSheet = EasyExcel.writerSheet(i, sheet.getSheetName())
.registerWriteHandler(new LongestMatchColumnWidthStyleStrategy())
.registerWriteHandler(new EasyExcelCellWriteHandler(map))
.registerWriteHandler(new ImportTempleRowWriteHandler())
.registerWriteHandler(new ImportTempleCellWriteHandler())
.head(sheet.getHeadClass())
.sheetName(sheet.getSheetName())
.relativeHeadRowIndex(RELATIVE_HEAD_ROW_INDEX)
.includeColumnFiledNames(sheet.getIncludeFiledNames())
.build();
}
excelWriter.write(sheet.getData(), writeSheet);
}
} catch (Exception e) {
Throwable cause = Throwables.getRootCause(e);
log.error("下载模板失败：{}", cause.getMessage(), cause);
throw new ServiceException("下载模板失败：{0}", cause.getMessage());
} finally {
if (excelWriter != null) {
excelWriter.finish();
}
}
} /**
* 批量导入 - 支持多sheet
*/
@SuppressWarnings("rawtypes")
public static Map<Class<?>, List<?>> readMultiSheet(MultipartFile file, Class<?>... classes) {
Map<Class<?>, List<?>> resultMap = Maps.newHashMapWithExpectedSize(classes.length + 1);
try {
checkExcelFile(file);
ByteArrayInputStream inputStream = deleteHiddenSheets(file);
ExcelReader excelReader = EasyExcel.read(inputStream).build();
for (int i = 0; i < classes.length; i++) {
Class clazz = classes[i];
SimpleAnalysisEventListener listener = SimpleAnalysisEventListener.factory(true);
ReadSheet readSheet = EasyExcel.readSheet(i)
.head(clazz)
.registerReadListener(listener)
.headRowNumber(headRowNumber(clazz))
.build();
excelReader.read(readSheet);
resultMap.put(clazz, listener.getResults());
}
if (resultMap.values().stream().allMatch(CollectionUtils::isEmpty)) {
throw new ServiceException("请至少录入一条数据");
}
} catch (Exception e) {
Throwable cause = Throwables.getRootCause(e);
log.error("解析异常：{}", cause.getMessage(), cause);
throw new ServiceException("解析异常：{0}", cause.getMessage());
}
return resultMap;
}
//删除导出模板时生成的隐藏sheet,避免导入时读取带隐藏sheet报错
public static ByteArrayInputStream deleteHiddenSheets(MultipartFile file){
try (InputStream inputStream = file.getInputStream();
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
){
Workbook workbook = new XSSFWorkbook(inputStream);
for (int i = 0; i < workbook.getNumberOfSheets(); i++) {
Sheet sheet = workbook.getSheetAt(i);
if (sheet.getSheetName().contains(EasyExcelCellWriteHandler.SHEET_NAME)) {
workbook.removeSheetAt(i);
i--; // 因为删除了一个sheet，索引需要调整
}
}
workbook.write(outputStream);
workbook.close();
return new ByteArrayInputStream(outputStream.toByteArray());
} catch (IOException e) {
log.error("解析excel失败！",e);
throw new ServiceException("解析失败！");
}
}
原生poi参考这位大佬：解决POI的SXSSFSheet 创建excel下拉框，下拉框内容过多时不显示的问题_java poi 下拉框数据7万行,隐藏sheet方法也看不不全-CSDN博客
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