poi导出excel根据列合并单元格

业务需求是要求把一个树结构的数据导出成excel格式的文件，大概是这样的：

 上代码：

/**
 *     用于保存需要合并的单元格
 */
public class MergeModel {
    private String content;//内容
    private int rowIndex;//记录相同内容的开始行号
    private int cellIndex;//列号
    public String getContent() {
        return content;
    }
    public void setContent(String content) {
        this.content = content;
    }
    public int getRowIndex() {
        return rowIndex;
    }
    public void setRowIndex(int rowIndex) {
        this.rowIndex = rowIndex;
    }
    public int getCellIndex() {
        return cellIndex;
    }
    public void setCellIndex(int cellIndex) {
        this.cellIndex = cellIndex;
    }
    
}

import java.io.FileOutputStream;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

import org.apache.poi.ss.usermodel.HorizontalAlignment;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.xssf.usermodel.XSSFCell;
import org.apache.poi.xssf.usermodel.XSSFCellStyle;
import org.apache.poi.xssf.usermodel.XSSFRow;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import poiExcel.model.MergeModel;

public class ExportExcel {
    /**
     *     创建excel文件
     * @param objData 数据
     * @param fileName 文件名
     * @param sheetName sheet名
     * @param columns 表头
     * @param mergeIndex 需要合并的列号集合
     * @return 
     */
    public static int exportToExcelForXlsx(List<List<Object>> objData,String fileName, String sheetName, List<String> columns,List<Integer> mergeIndex) {
        int flag = 0;
        
        // 创建工作薄
        XSSFWorkbook wb = new XSSFWorkbook();
        // sheet1
        XSSFSheet sheet1 = wb.createSheet(sheetName);
        
        //设置样式
        XSSFCellStyle style = wb.createCellStyle();
        style.setAlignment(HorizontalAlignment.CENTER);//水平对齐
        
        //表头
        sheet1.createFreezePane(0, 1);//冻结表头
        XSSFRow sheet1row1 = sheet1.createRow((short) 0);
        sheet1row1.setHeight((short) 480);
        //写入表头
        if (columns != null && columns.size() > 0) {
            for(int i=0;i<columns.size();i++) {
                String column = columns.get(i);
                //列
                XSSFCell cell = sheet1row1.createCell(i);
                cell.setCellValue(column);
            }
        }
        
        int dataSatrtIndex = 1;//数据开始行
        boolean isMerge = false;
        if(mergeIndex != null && mergeIndex.size() != 0) {
            isMerge = true;
        }
        
        //写入数据
        if (objData != null && objData.size() > 0) {
            Map<Integer,MergeModel> poiModels = new HashMap<Integer, MergeModel>();
            
            //循环写入表中数据
            int i = 0;
            for ( ; i < objData.size(); i++) {
                //数据行
                XSSFRow row = sheet1.createRow((short) (i+dataSatrtIndex));
                //行内循环，既单元格（列）
                List<Object> list = objData.get(i);
                DecimalFormat decimalFormat = new DecimalFormat("0.00");
                int j = 0;
                for (Object o : list) {
                    //数据列
                    String content = "";
                    if(o != null) {
                        if (o.toString().contains(".") && isNumeric(o.toString())) {
                            content = decimalFormat.format(Float.valueOf(o.toString()));
                        } else if (o.toString().contains("-") && o.toString().contains(":")) {
                            content = String.valueOf(o).split("\\.")[0];
                        }else {
                            content = String.valueOf(o);
                        }
                    }
                    
                    if(isMerge && mergeIndex.contains(j)) {
                        //如果该列需要合并
                        MergeModel poiModel = poiModels.get(j);
                        if(poiModel == null) {
                            poiModel = new MergeModel();
                            poiModel.setContent(content);
                            poiModel.setRowIndex(i + dataSatrtIndex);
                            poiModel.setCellIndex(j);
                            poiModels.put(j, poiModel);
                        }else {
                            if(!poiModel.getContent().equals(content)) {
                                //如果不同了，则将前面的数据合并写入
                                XSSFRow lastRow = sheet1.getRow(poiModel.getRowIndex());
                                XSSFCell lastCell = lastRow.createCell(poiModel.getCellIndex());//创建列
                                lastCell.setCellValue(poiModel.getContent());
                                //合并单元格
                                if(poiModel.getRowIndex() != i + dataSatrtIndex - 1) {
                                    sheet1.addMergedRegion(new CellRangeAddress(poiModel.getRowIndex(), i + dataSatrtIndex - 1, poiModel.getCellIndex(), poiModel.getCellIndex()));
                                }
                                //将新数据存入
                                poiModel.setContent(content);
                                poiModel.setRowIndex(i + dataSatrtIndex);
                                poiModel.setCellIndex(j);
                                poiModels.put(j, poiModel);
                            }
                        }
                        row.createCell(j);//创建单元格
                    }else {//该列不需要合并
                        //数据列
                        XSSFCell cell = row.createCell(j);
                        cell.setCellValue(content);
                    }
                    
                    j++;
                }
            
            }
            
            //将最后一份存入
            if(poiModels != null && poiModels.size() != 0) {
                for(Integer key : poiModels.keySet()) {
                    MergeModel poiModel = poiModels.get(key);
                    XSSFRow lastRow = sheet1.getRow(poiModel.getRowIndex());
                    XSSFCell lastCell = lastRow.getCell(poiModel.getCellIndex());
                    lastCell.setCellValue(poiModel.getContent());
                    //合并单元格
                    if(poiModel.getRowIndex() != i + dataSatrtIndex -1) {
                        sheet1.addMergedRegion(new CellRangeAddress(poiModel.getRowIndex(), i + dataSatrtIndex - 1, poiModel.getCellIndex(), poiModel.getCellIndex()));
                    }
                }
            }
        } else {
            flag = -1;
        }
        
        //设置固定列宽，poi的列宽设置有点操蛋，大概规律网上有不少版本自行百度
        //这里大概是143像素
        for (int i = 0; i < columns.size(); i++) {
            sheet1.setColumnWidth(i, 4550);
        }
        
        FileOutputStream out = null;  
        try {    
            out = new FileOutputStream("E:\\" + fileName + ".xlsx");
            wb.write(out);
        } catch (Exception ex) {
            try {  
                out.flush();  
                out.close();  
            }catch (IOException e){  
                e.printStackTrace();  
            }  
        }
        return flag;
    }
    
    /**
     *     判断是不是数字
     * @param str
     * @return 
     */
    private static boolean isNumeric(String str){
        if(str == null || str.length() == 0) {
            return false;
        }
        Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$"); 
        return pattern.matcher(str).matches();
    }
}

import java.util.ArrayList;
import java.util.List;

import poiExcel.utils.ExportExcel;

public class Startover {
    public static void main(String[] args) {
         List<String> columns = new ArrayList<>();//标头
         columns.add("目录");
         columns.add("目录");
         columns.add("目录");
         columns.add("内容");
         String fileName = "文件名字";//文件名字
         String sheetName = "sheet名字";//sheet名字
         //内容数据
         List<List<Object>> exportData = new ArrayList<>();
         //行内的数据
         List<Object> rowData = new ArrayList<Object>();
         rowData.add("一级目录1");
         rowData.add("二级目录1");
         rowData.add("三级目录1");
         rowData.add("内容1");
         exportData.add(rowData);
         List<Object> rowData2 = new ArrayList<Object>();
         rowData2.add("一级目录1");
         rowData2.add("二级目录1");
         rowData2.add("三级目录1");
         rowData2.add("内容2");
         exportData.add(rowData2);
         List<Object> rowData3 = new ArrayList<Object>();
         rowData3.add("一级目录1");
         rowData3.add("二级目录1");
         rowData3.add("三级目录2");
         rowData3.add("内容3");
         exportData.add(rowData3);
         List<Object> rowData4 = new ArrayList<Object>();
         rowData4.add("一级目录1");
         rowData4.add("二级目录1");
         rowData4.add("三级目录2");
         rowData4.add("内容4");
         exportData.add(rowData4);
         List<Object> rowData5 = new ArrayList<Object>();
         rowData5.add("一级目录1");
         rowData5.add("二级目录2");
         rowData5.add("三级目录3");
         rowData5.add("内容5");
         exportData.add(rowData5);
         List<Object> rowData6 = new ArrayList<Object>();
         rowData6.add("一级目录1");
         rowData6.add("二级目录2");
         rowData6.add("三级目录3");
         rowData6.add("内容6");
         exportData.add(rowData6);
         //需要合并的列号
         List<Integer> mergeIndex = new ArrayList<Integer>();
         mergeIndex.add(0);
         mergeIndex.add(1);
         mergeIndex.add(2);
         int flag = ExportExcel.exportToExcelForXlsx(exportData, fileName, sheetName, columns, mergeIndex);
         System.out.println(flag);
    }
}