1：配置pom下的依赖

		<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.poi</groupId>
            <artifactId>poi-ooxml</artifactId>
            <version>4.1.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>5.3.23</version>
        </dependency>
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-core</artifactId>
            <version>9.0.68</version>
        </dependency>

2：编写请求下载类

package com.example.poi;

import org.apache.poi.ss.usermodel.*;
import org.apache.poi.ss.util.CellRangeAddress;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @Author xu
 * @create 2023/7/5 01
 */

@RequestMapping("/custom")
public class Demo {
    @GetMapping("/export")
    public void exportExcel(HttpServletResponse response) {

        List<Map<String, Object>> studentList = new ArrayList<>();
        Map<String, Object> student1 = new HashMap<>();
        student1.put("姓名", "张三");
        student1.put("年龄", 18);
        student1.put("成绩", 99);

        Map<String, Object> student2 = new HashMap<>();
        student2.put("姓名", "李四");
        student2.put("年龄", 20);
        student2.put("成绩", 100);

        studentList.add(student1);
        studentList.add(student2);

        Workbook workbook = new XSSFWorkbook();
        Sheet sheet = workbook.createSheet("学生信息");


        // 创建标题行
        Row titleRow = sheet.createRow(0);
        Cell titleCell = titleRow.createCell(0);
        titleCell.setCellValue("这是标题");

        // 合并标题行的单元格，重点这里的参数，可以选择合并的情况，然后再设置字体样式都可以
        sheet.addMergedRegion(new CellRangeAddress(1, 1, 0, 2));

        // 设置标题样式
        CellStyle titleStyle = workbook.createCellStyle();
        Font font = workbook.createFont();
        titleStyle.setFont(font);
        titleStyle.setAlignment(HorizontalAlignment.CENTER);
        titleCell.setCellStyle(titleStyle);

        // 写入表头
        Row headerRow = sheet.createRow(1);
        int columnIndex = 0;
        for (String key : studentList.get(0).keySet()) {
            Cell cell = headerRow.createCell(columnIndex++);
            cell.setCellValue(key);
        }

        // 写入数据
        int rowIndex = 1;
        for (Map<String, Object> student : studentList) {
            Row dataRow = sheet.createRow(rowIndex++);
            columnIndex = 0;
            for (Object value : student.values()) {
                Cell cell = dataRow.createCell(columnIndex++);
                cell.setCellValue(value.toString());
            }
        }

        try {
            response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
            response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode("学生信息表12.xlsx", "UTF-8"));
            workbook.write(response.getOutputStream());
            workbook.close();
        } catch (
                IOException e) {
            e.printStackTrace();
        }
    }
}