poi实现下拉多选

Apache POI 本身并不提供下拉多选的功能，但可以通过设置数据验证实现类似的效果。具体步骤如下：

1. 创建下拉列表的选项

DataValidationHelper validationHelper = new XSSFDataValidationHelper(sheet);
XSSFDataValidationConstraint dvConstraint = (XSSFDataValidationConstraint) validationHelper.createExplicitListConstraint(new String[]{"选项1", "选项2", "选项3"});

2. 创建数据验证对象并设置验证范围

CellRangeAddressList addressList = new CellRangeAddressList(0, 0, 0, 0);
XSSFDataValidation validation = (XSSFDataValidation) validationHelper.createValidation(dvConstraint, addressList);

3. 设置多选模式

validation.setValidationType(ValidationType.LIST);
validation.setShowErrorBox(true);
validation.setErrorStyle(DataValidation.ErrorStyle.STOP);
validation.createPromptBox("提示", "请选择多个选项");
validation.setShowPromptBox(true);

4. 将数据验证对象添加到工作表中

sheet.addValidationData(validation);

完整代码示例：

import java.io.FileOutputStream;
import org.apache.poi.ss.usermodel.DataValidation;
import org.apache.poi.ss.usermodel.DataValidationHelper;
import org.apache.poi.ss.usermodel.DataValidationConstraint.ValidationType;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.util.CellRangeAddressList;
import org.apache.poi.xssf.usermodel.XSSFDataValidation;
import org.apache.poi.xssf.usermodel.XSSFDataValidationHelper;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class MultiSelectDropDownExample {
    public static void main(String[] args) throws Exception {
        Workbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet("Sheet1");

        // create drop down options
        DataValidationHelper validationHelper = new XSSFDataValidationHelper(sheet);
        XSSFDataValidationConstraint dvConstraint = (XSSFDataValidationConstraint) validationHelper.createExplicitListConstraint(new String[]{"Option 1", "Option 2", "Option 3"});

        // create data validation and set range
        CellRangeAddressList addressList = new CellRangeAddressList(0, 0, 0, 0);
        XSSFDataValidation validation = (XSSFDataValidation) validationHelper.createValidation(dvConstraint, addressList);

        // set multi-select mode
        validation.setValidationType(ValidationType.LIST);
        validation.setShowErrorBox(true);
        validation.setErrorStyle(DataValidation.ErrorStyle.STOP);
        validation.createPromptBox("Prompt", "Please select multiple options");
        validation.setShowPromptBox(true);

        // add data validation to sheet
        sheet.addValidationData(validation);

        FileOutputStream fileOut = new FileOutputStream("multi_select_dropdown.xlsx");
        workbook.write(fileOut);
        fileOut.close();

        System.out.println("Excel file created!");
    }
}