Java将Map及实体类转化为Excel（支持合并行）

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.util.List;
import java.util.Map;
 
public class ExcelUtil {
 
    public static <T> void createExcel(List<T> dataList, Class<T> cls, Map<String, Integer> mergeMap, String fileName) throws IOException {
        Workbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet();
 
        // 创建标题行
        Row titleRow = sheet.createRow(0);
        Field[] fields = cls.getDeclaredFields();
        for (int i = 0; i < fields.length; i++) {
            titleRow.createCell(i).setCellValue(fields[i].getName());
        }
 
        // 填充数据
        int rowIndex = 1;
        for (T data : dataList) {
            Row dataRow = sheet.createRow(rowIndex);
            for (int i = 0; i < fields.length; i++) {
                Field field = fields[i];
                field.setAccessible(true);
                try {
                    Object value = field.get(data);
                    dataRow.createCell(i).setCellValue(value == null ? "" : value.toString());
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
            rowIndex++;
        }
 
        // 合并行
        for (Map.Entry<String, Integer> mergeEntry : mergeMap.entrySet()) {
            String[] mergeInfo = mergeEntry.getKey().split("-");
            int firstRow = Integer.parseInt(mergeInfo[0]);
            int lastRow = Integer.parseInt(mergeInfo[1]);
            int col = mergeEntry.getValue();
            sheet.addMergedRegion(new CellRangeAddress(firstRow, lastRow, col, col));
        }
 
        // 写入文件
        FileOutputStream out = new FileOutputStream(fileName);
        workbook.write(out);
        out.close();
        workbook.close(