Java uses Apache.POI to export HSSFWorkbook to Excel

<dependency>
   <groupId>org.apache.poi</groupId>
   <artifactId>poi</artifactId>
   <version>3.12</version>
</dependency>

package com.kd.nm.entity.pojo;

/**
 * Entity class (User)
 *
 * author Xiaochen Gege*/
public class User {
 // User number private String userNo;
 //User nameprivate String userName;
 //Ageprivate String age;

 // No parameter construction public User() {
 }

 // Constructor with parameters public User(String userNo, String userName, String age) {
  this.userNo = userNo;
  this.userName = userName;
  this.age = age;
 }

 // Encapsulate get and set methods public String getUserNo() {
  return userNo;
 }

 public void setUserNo(String userNo) {
  this.userNo = userNo;
 }

 public String getUserName() {
  return userName;
 }

 public void setUserName(String userName) {
  this.userName = userName;
 }

 public String getAge() {
  return age;
 }

 public void setAge(String age) {
  this.age = age;
 }

 //Rewrite toString method @Override
 public String toString() {
  return "User{" +
    "userNo='" + userNo + '\'' +
    ", userName='" + userName + '\'' +
    ", age='" + age + '\'' +
    '}';
 }
}

package com.kd.nm.util;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.apache.poi.hssf.usermodel.*;

/**
 * Description: Excel related tools*
 * @author: Brother Xiaochen*
 */
public class ExcelUtil {

 /**
  * Generate excel table* @param heads header content* @param data data content* @return
  */
 public static HSSFWorkbook createExcel(Map<String, String> heads, List data) {

  //Declare a workbook HSSFWorkbook workbook = new HSSFWorkbook();
  // Generate a table HSSFSheet sheet = workbook.createSheet();

  // Generate title row style HSSFCellStyle headStyle = creatStyle(workbook, (short) 14);

  // Generate table content style HSSFCellStyle bodyStyle = creatStyle(workbook, (short) 10);

  // Title elements List<String> keys = new ArrayList<String>(heads.keySet());

  // Pixel unit short px = 1000;
  // Set column width for (int columnIndex = 0; columnIndex < keys.size(); columnIndex++) {

   sheet.setColumnWidth(columnIndex, 6 * px);
  }

  // Generate table for (int rowNum = 0; rowNum <= data.size(); rowNum++) {

   // Create row HSSFRow row = sheet.createRow(rowNum);

   for (int cellNum = 0; cellNum < keys.size(); cellNum++) {

    // Create column HSSFCell cell = row.createCell(cellNum);

    // Title if (rowNum == 0) {

     cell.setCellStyle(headStyle);
     cell.setCellValue(heads.get(keys.get(cellNum)));
    } else { // Content cell.setCellStyle(bodyStyle);
     // Get cell through reflection.setCellValue(ReflectUtil.getValue(keys.get(cellNum), data.get(rowNum - 1)));
    }
   }
  }

  return workbook;
 }

 /**
  * Generate style * @param workbook
  * @param size
  * @return
  */
 public static HSSFCellStyle creatStyle(HSSFWorkbook workbook, short size) {

  HSSFCellStyle style = workbook.createCellStyle();
  style.setAlignment((HSSFCellStyle.ALIGN_CENTER));
  style.setVerticalAlignment((HSSFCellStyle.VERTICAL_CENTER));
  HSSFFont font = workbook.createFont();
  font.setFontHeightInPoints(size);
  font.setFontName("Microsoft YaHei");
  style.setFont(font);
  style.setBorderBottom(HSSFCellStyle.BORDER_THIN);
  style.setBorderTop(HSSFCellStyle.BORDER_THIN);
  style.setBorderRight(HSSFCellStyle.BORDER_THIN);
  style.setBorderLeft(HSSFCellStyle.BORDER_THIN);

  return style;
 }
}

package com.kd.nm.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ReflectionUtils;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;

/**
 * Reflection Toolkit*
 * @author: Brother Xiaochen*/
public class ReflectUtil {

 private static final Logger logger = LoggerFactory.getLogger(ReflectUtil.class);

 public static String getValue(String key, Object obj) {

  String value = "";

  try {

   // Get the current property PropertyDescriptor pd = new PropertyDescriptor(key, obj.getClass());
   // Get the get method Method getMd = pd.getReadMethod();
   value = getMd.invoke(obj).toString();
  } catch (Exception e) {

   logger.error("Failed to get content!");
   e.printStackTrace();
  }

  return value;
 }

 public static void setValue(String key, String value, Object obj) {

  try {

   // Get the current property PropertyDescriptor pd = new PropertyDescriptor(key, obj.getClass());
   // Get the set method Method writeMd = pd.getWriteMethod();
   writeMd.invoke(obj, value);
  } catch (Exception e) {

   logger.error("Failed to set content!");
   e.printStackTrace();
  }
 }
}

@RequestMapping(value = "/exportExcel",method = RequestMethod.GET,produces = "application/json")
 public void exportExcel(HttpServletResponse httpServletResponse) throws IOException {

  // Header content (can be set on the front end and passed in via parameters) Key is the attribute value of the entity class, value is the label of the header
  Map<String,String> head = new HashMap<>();
  head.put("userNo","User No.");
  head.put("userName","user name");
  head.put("age","age");

  //Table data content, simulating the data queried from the database List<User> data = new ArrayList<>();
  data.add(new User("1","Little Chen's brother","18"));
  data.add(new User("2","Little Piggy Sister","18"));
  data.add(new User("3","Big Pig Brother","18"));
  
  
  // Generate workbook HSSFWorkbook hssfWorkbook = ExcelUtil.createExcel(head, data);

  // Define the file name String fileName = "Export Excel table";

  httpServletResponse.setHeader("Cache-Control", "max-age=0");
  httpServletResponse.setContentType("application/vnd.ms-excel");
  httpServletResponse.addHeader("Content-disposition", "attachment;filename=" + new String(fileName.getBytes("gb2312"),
    "ISO-8859-1") + ".xls");

  OutputStream outputStream = httpServletResponse.getOutputStream();

  hssfWorkbook.write(outputStream);
  outputStream.flush();
  outputStream.close();
 }