java eazyexcel 实现excel的动态多级联动下拉列表（1）使用名称管理器+INDIRECT函数

原理

1. 将数据源放到一个新建的隐藏的sheet中
2. 将选项的子选项的对应字典设置到名称管理器中（名称是当前选项的内容，值是他对应的子菜单的单元格范围，在1里面的sheet中）
3. 子菜单的数据根据INDIRECT函数去左边那个单元格获取内容，根据内容去名称管理器中获取字典的key，也就是子菜单的单元格范围
4. 使用方式只需要构建CascadeCellBO对象即可，定义级联初始位置和行数，还有选项列表nameCascadeList，他的结构很简单就是name和子nameCascadeList。代码会自动扫描出最深的子菜单层数，根据这个层数构建下拉的个数

优缺点

优点

选项的个数和内容的个数不限制

缺点

1. 因为excel的名称管理器的名称有很多限制比如不支持特殊字符、不支持括号、不能数字开头等等，所以选项的内容也会有这些限制
2. 因为excel的名称管理器的名称不能相同，所有如果有两个相同二级菜单在不同的一级菜单中，那这两个二级菜单的三级菜单会是一样的

总之使用名称管理器+INDIRECT函数实现的级联下拉列表，只能做一些简单的数据，如果想克服那些缺点，需要用另一种方式，请看下篇文章

代码

import lombok.Data;

import java.util.List;

/**
 * @date 2024-01-19 21:05
 */
@Data
public class CascadeCellBO {

    /**
     * 初始的行
     */
    private int rowIndex;

    /**
     * 初始的列
     */
    private int colIndex;

    /**
     * 行数
     */
    private int rowNum;

    /**
     * 选项
     */
    private List<NameCascadeBO> nameCascadeList;
}

import lombok.Data;

import java.util.List;

/**
 * @date 2024-01-20 10:26
 */
@Data
public class NameCascadeBO {
    /**
     * 名称
     */
    private String name;

    /**
     * 子选项
     */
    private List<NameCascadeBO> nameCascadeList;
}

import com.alibaba.excel.write.handler.SheetWriteHandler;
import com.alibaba.excel.write.metadata.holder.WriteSheetHolder;
import com.alibaba.excel.write.metadata.holder.WriteWorkbookHolder;
import lombok.Data;
import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddressList;

import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.stream.IntStream;

@Data
public class CascadeWriteHandler implements SheetWriteHandler {

    private final String dataSourceName;

    private final CascadeCellBO cascadeCellBO;

    public CascadeWriteHandler(CascadeCellBO cascadeCellBO) {
        this.cascadeCellBO = cascadeCellBO;
        this.dataSourceName = "dataSource" + System.currentTimeMillis();
    }

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

    }

    @Override
    public void afterSheetCreate(WriteWorkbookHolder writeWorkbookHolder, WriteSheetHolder writeSheetHolder) {
        //获取工作簿
        Sheet sheet = writeSheetHolder.getSheet();
        Workbook book = writeWorkbookHolder.getWorkbook();
        //创建一个专门用来存放地区信息的隐藏sheet页
        //因此不能在现实页之前创建，否则无法隐藏。
        Sheet hideSheet = book.createSheet(dataSourceName);
        book.setSheetHidden(book.getSheetIndex(hideSheet), true);
        // 将具体的数据写入到每一行中，每行的第一个单元格为父级区域的值，后面是子区域。
        List<NameCascadeBO> nameCascadeList = cascadeCellBO.getNameCascadeList();
        if (nameCascadeList == null || nameCascadeList.isEmpty()) {
            return;
        }

        Row row = hideSheet.createRow(0);
        IntStream.range(0, nameCascadeList.size()).forEach(i ->
                row.createCell(i).setCellValue(nameCascadeList.get(i).getName()));

        // 大类规则
        int colIndex = cascadeCellBO.getColIndex();
        int firstRowIndex = cascadeCellBO.getRowIndex();
        int lastRowIndex = firstRowIndex + cascadeCellBO.getRowNum();

        ///开始设置（大类小类）下拉框
        DataValidationHelper dvHelper = sheet.getDataValidationHelper();
        CellRangeAddressList expRangeAddressList = new CellRangeAddressList(firstRowIndex, lastRowIndex, colIndex, colIndex);
        String bigEndCol = colIndex2Str(nameCascadeList.size());
        DataValidationConstraint bigFormula = dvHelper.createFormulaListConstraint("=" + dataSourceName + "!$A$1:$" + bigEndCol + "$1");
        setValidation(sheet, dvHelper, bigFormula, expRangeAddressList, "提示", "你输入的值未在备选列表中，请下拉选择合适的值");

        // 小类规则(各单元格按个设置)
        // "INDIRECT($A$" + 2 + ")" 表示规则数据会从名称管理器中获取key与单元格 A2 值相同的数据，如果A2是浙江省，那么此处就是浙江省下面的市
        // 为了让每个单元格的公式能动态适应，使用循环挨个给公式。
        // 循环几次，就有几个单元格生效，次数要和上面的大类影响行数一一对应，要不然最后几个没对上的单元格实现不了级联
        AtomicInteger rowId = new AtomicInteger(1);
        buildName(book, hideSheet, nameCascadeList, rowId);
        int maxLevel = getMaxLevel(nameCascadeList, 0);
        for (int num = 1; num < maxLevel; num++) {
            String start = colIndex2Str(colIndex + num);
            String preStart = "$" + start + "$";
            for (int i = firstRowIndex; i <= lastRowIndex; i++) {
                CellRangeAddressList rangeAddressList = new CellRangeAddressList(i, i, colIndex + num, colIndex + num);
                DataValidationConstraint formula = dvHelper.createFormulaListConstraint("INDIRECT(" + preStart + (i + 1) + ")");
                setValidation(sheet, dvHelper, formula, rangeAddressList, "提示", "你输入的值未在备选列表中，请下拉选择合适的值");
            }
        }
    }

    // 添加名称管理器
    private void buildName(Workbook book, Sheet hideSheet, List<NameCascadeBO> nameCascadeList, AtomicInteger rowId) {
        Optional.ofNullable(nameCascadeList).ifPresent(l -> l.forEach(nameCascadeBO -> {
            List<NameCascadeBO> childList = nameCascadeBO.getNameCascadeList();
            if (childList != null && !childList.isEmpty()) {
                Row row = hideSheet.createRow(rowId.getAndIncrement());
                row.createCell(0).setCellValue(nameCascadeBO.getName());
                IntStream.range(0, childList.size()).forEach(c ->
                        row.createCell(c + 1).setCellValue(childList.get(c).getName()));
                // 添加名称管理器
                String endCol = colIndex2Str(1 + childList.size());
                String range = "$B$" + rowId.get() + ":$" + endCol + "$" + rowId.get();

                Name name = book.createName();
                name.setNameName(nameCascadeBO.getName());
                name.setRefersToFormula(dataSourceName + "!" + range);
                buildName(book, hideSheet, childList, rowId);
            }
        }));
    }

    private int getMaxLevel(List<NameCascadeBO> nameCascadeList, int preLevel) {
        int curLevel = preLevel + 1;
        int maxLevel = curLevel;
        for (NameCascadeBO nameCascadeBO : nameCascadeList) {
            List<NameCascadeBO> childList = nameCascadeBO.getNameCascadeList();
            if (childList != null && !childList.isEmpty()) {
                int level = getMaxLevel(childList, curLevel);
                maxLevel = Math.max(level, maxLevel);
            }
        }
        return maxLevel;
    }

    /**
     * 设置验证规则
     *
     * @param sheet       sheet对象
     * @param helper      验证助手
     * @param constraint  createExplicitListConstraint
     * @param addressList 验证位置对象
     * @param msgHead     错误提示头
     * @param msgContext  错误提示内容
     */
    private void setValidation(Sheet sheet, DataValidationHelper helper, DataValidationConstraint constraint, CellRangeAddressList addressList, String msgHead, String msgContext) {
        DataValidation dataValidation = helper.createValidation(constraint, addressList);
        dataValidation.setErrorStyle(DataValidation.ErrorStyle.STOP);
        dataValidation.setShowErrorBox(true);
        dataValidation.setSuppressDropDownArrow(true);
        dataValidation.createErrorBox(msgHead, msgContext);
        sheet.addValidationData(dataValidation);
    }

    public static String colIndex2Str(int column) {
        if (column <= 0) {
            return null;
        }
        String columnStr = "";
        column--;
        do {
            if (columnStr.length() > 0) {
                column--;
            }
            columnStr = ((char) (column % 26 + (int) 'A')) + columnStr;
            column = (int) ((column - column % 26) / 26);
        } while (column > 0);
        return columnStr;
    }
}

使用

public static void main(String[] args) {
        List<List<String>> header = new ArrayList<>();
        header.add(Arrays.asList( "sc2"));
        header.add(Arrays.asList( "sc3"));
        int colIndex = header.size() - 1;
        List<NameCascadeBO> nameCascadeList = new ArrayList<>();
        NameCascadeBO nameCascadeBO = new NameCascadeBO();
        nameCascadeBO.setName("第一层1");

        List<NameCascadeBO> nameCascadeList2 = new ArrayList<>();
        NameCascadeBO nameCascadeBO2 = new NameCascadeBO();
        nameCascadeBO2.setName("第二层11");

        List<NameCascadeBO> nameCascadeList3 = new ArrayList<>();
        IntStream.range(0, 400).forEach(i -> {
            NameCascadeBO nameCascadeBO3 = new NameCascadeBO();
            nameCascadeBO3.setName("第三层11" + i);
            nameCascadeList3.add(nameCascadeBO3);
        });

        nameCascadeBO2.setNameCascadeList(nameCascadeList3);
        nameCascadeList2.add(nameCascadeBO2);

        nameCascadeBO2 = new NameCascadeBO();
        nameCascadeBO2.setName("第二层12");
        nameCascadeList2.add(nameCascadeBO2);

        nameCascadeBO.setNameCascadeList(nameCascadeList2);
        nameCascadeList.add(nameCascadeBO);

        nameCascadeBO = new NameCascadeBO();
        nameCascadeBO.setName("第一层2");

        nameCascadeList2 = new ArrayList<>();
        nameCascadeBO2 = new NameCascadeBO();
        nameCascadeBO2.setName("第二层21");
        nameCascadeList2.add(nameCascadeBO2);

        nameCascadeBO2 = new NameCascadeBO();
        nameCascadeBO2.setName("第二层22");
        nameCascadeList2.add(nameCascadeBO2);

        nameCascadeBO.setNameCascadeList(nameCascadeList2);
        nameCascadeList.add(nameCascadeBO);

        IntStream.range(2, 200).forEach(i -> {
            NameCascadeBO item = new NameCascadeBO();
            item.setName("第一层" + i);
            nameCascadeList.add(item);
        });


        CascadeCellBO cascadeCellBO = new CascadeCellBO();
        cascadeCellBO.setRowIndex(2);
        cascadeCellBO.setRowNum(10);
        cascadeCellBO.setColIndex(colIndex);
        cascadeCellBO.setNameCascadeList(nameCascadeList);
        CascadeWriteHandler cascadeWriteHandler = new CascadeWriteHandler(cascadeCellBO);

        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        EasyExcelFactory.write(outputStream).head(header)
                .registerWriteHandler(cascadeWriteHandler)
                .sheet("导入信息").doWrite(new ArrayList<>());

        FileUtils.save2File("/Users/admin/aa/导入模板.xlsx", outputStream.toByteArray());
    }