java poi写一个Excel导出，导出对象类型是List<People> peopleList有5个属性, People对象中有两个属性为List<Son> sonList，List<dog> dogList。导出的Excel表头为peopleList中三个普通字段和List<Son>、List<dog>为一级表头，sonList、dogList中的属性为List<Son> sonList、List<dog> dogList下的二级表头

好的，首先你需要添加以下依赖：

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>4.1.2</version>
</dependency>

然后，你可以按照以下步骤编写代码：

1. 创建一个 Workbook 对象，这里我们使用 XSSFWorkbook。

Workbook workbook = new XSSFWorkbook();

2. 创建一个 Sheet 对象，并设置表头。

Sheet sheet = workbook.createSheet("peopleList");

Row headerRow = sheet.createRow(0);

Cell cell = headerRow.createCell(0);
cell.setCellValue("姓名");

cell = headerRow.createCell(1);
cell.setCellValue("年龄");

cell = headerRow.createCell(2);
cell.setCellValue("性别");

int columnIndex = 3;
for (int i = 0; i < peopleList.size(); i++) {
    People people = peopleList.get(i);
    for (Son son : people.getSonList()) {
        for (Dog dog : people.getDogList()) {
            String sonName = son.getName();
            String dogName = dog.getName();

            cell = headerRow.createCell(columnIndex++);
            cell.setCellValue(sonName + "-" + dogName + "-" + "名称");

            cell = headerRow.createCell(columnIndex++);
            cell.setCellValue(sonName + "-" + dogName + "-" + "颜色");

            cell = headerRow.createCell(columnIndex++);
            cell.setCellValue(sonName + "-" + dogName + "-" + "年龄");
        }
    }
}

3. 遍历 List<People>，并将数据写入 Excel 中。

int rowIndex = 1;
for (People people : peopleList) {
    Row row = sheet.createRow(rowIndex++);

    cell = row.createCell(0);
    cell.setCellValue(people.getName());

    cell = row.createCell(1);
    cell.setCellValue(people.getAge());

    cell = row.createCell(2);
    cell.setCellValue(people.getGender());

    columnIndex = 3;
    for (Son son : people.getSonList()) {
        for (Dog dog : people.getDogList()) {
            String sonName = son.getName();
            String dogName = dog.getName();
            String sonColor = son.getColor();
            String dogColor = dog.getColor();
            int sonAge = son.getAge();
            int dogAge = dog.getAge();

            cell = row.createCell(columnIndex++);
            cell.setCellValue(sonName);

            cell = row.createCell(columnIndex++);
            cell.setCellValue(sonColor);

            cell = row.createCell(columnIndex++);
            cell.setCellValue(sonAge);

            cell = row.createCell(columnIndex++);
            cell.setCellValue(dogName);

            cell = row.createCell(columnIndex++);
            cell.setCellValue(dogColor);

            cell = row.createCell(columnIndex++);
            cell.setCellValue(dogAge);
        }
    }
}

4. 最后，将 Excel 数据写入输出流中。

response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "attachment;filename=peopleList.xlsx");

OutputStream outputStream = response.getOutputStream();
workbook.write(outputStream);
outputStream.flush();
outputStream.close();

完整代码如下：

import org.apache.poi.ss.usermodel.*;

import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;

public class PeopleExcelExportUtil {

    public static void export(HttpServletResponse response, List<People> peopleList) throws IOException {
        Workbook workbook = new XSSFWorkbook();

        Sheet sheet = workbook.createSheet("peopleList");

        Row headerRow = sheet.createRow(0);

        Cell cell = headerRow.createCell(0);
        cell.setCellValue("姓名");

        cell = headerRow.createCell(1);
        cell.setCellValue("年龄");

        cell = headerRow.createCell(2);
        cell.setCellValue("性别");

        int columnIndex = 3;
        for (int i = 0; i < peopleList.size(); i++) {
            People people = peopleList.get(i);
            for (Son son : people.getSonList()) {
                for (Dog dog : people.getDogList()) {
                    String sonName = son.getName();
                    String dogName = dog.getName();

                    cell = headerRow.createCell(columnIndex++);
                    cell.setCellValue(sonName + "-" + dogName + "-" + "名称");

                    cell = headerRow.createCell(columnIndex++);
                    cell.setCellValue(sonName + "-" + dogName + "-" + "颜色");

                    cell = headerRow.createCell(columnIndex++);
                    cell.setCellValue(sonName + "-" + dogName + "-" + "年龄");
                }
            }
        }

        int rowIndex = 1;
        for (People people : peopleList) {
            Row row = sheet.createRow(rowIndex++);

            cell = row.createCell(0);
            cell.setCellValue(people.getName());

            cell = row.createCell(1);
            cell.setCellValue(people.getAge());

            cell = row.createCell(2);
            cell.setCellValue(people.getGender());

            columnIndex = 3;
            for (Son son : people.getSonList()) {
                for (Dog dog : people.getDogList()) {
                    String sonName = son.getName();
                    String dogName = dog.getName();
                    String sonColor = son.getColor();
                    String dogColor = dog.getColor();
                    int sonAge = son.getAge();
                    int dogAge = dog.getAge();

                    cell = row.createCell(columnIndex++);
                    cell.setCellValue(sonName);

                    cell = row.createCell(columnIndex++);
                    cell.setCellValue(sonColor);

                    cell = row.createCell(columnIndex++);
                    cell.setCellValue(sonAge);

                    cell = row.createCell(columnIndex++);
                    cell.setCellValue(dogName);

                    cell = row.createCell(columnIndex++);
                    cell.setCellValue(dogColor);

                    cell = row.createCell(columnIndex++);
                    cell.setCellValue(dogAge);
                }
            }
        }

        response.setContentType("application/vnd.ms-excel");
        response.setHeader("Content-disposition", "attachment;filename=peopleList.xlsx");

        OutputStream outputStream = response.getOutputStream();
        workbook.write(outputStream);
        outputStream.flush();
        outputStream.close();
    }

}