pom.xml:

    <dependency>
      <groupId>org.apache.poi</groupId>
      <artifactId>poi</artifactId>
      <version>3.6</version>
    </dependency>

工具類：

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

import java.lang.reflect.Field;
import java.util.HashMap;
import
 
 java.util.List;
import java.util.Map;

/**
 * Excel匯出工具類
 * @author 單繼重
 * @since 2017/11/23 16:44
 */
public class ExcelUtil {

    private static Map<String,String> exportFields = new HashMap<String, String>();

    //初始化屬性Map
    static {
        exportFields.put("name","活動名稱");
        exportFields.put("content"
 
,"活動內容");
        exportFields.put("population","活動人數");
        exportFields.put("provideMeal","提供餐飲");
        exportFields.put("provideHotel","提供住宿");
        exportFields.put("organization","主辦單位");
        exportFields.put("tel","電話");
        exportFields.put("qq","負責人qq");
        exportFields.put("time"
 
,"活動時間");
        exportFields.put("budget","活動經費");
        exportFields.put("certificate","活動證書");
        exportFields.put("status","活動狀態");
    }

    /**
     * 獲取Excel實體
     * @param sheetName sheet名字
     * @param list 物件集合
     * @return Excel實體
     * @throws IllegalAccessException 安全許可權異常
     */
    public static HSSFWorkbook getHSSFWorkbook(String sheetName, List list) throws IllegalAccessException {

        //獲取物件所有屬性
        Field[] fields = list.get(0).getClass().getDeclaredFields();

        //表頭陣列
        String[] title = new String[fields.length];

        //設定表頭
        for (int i = 0 ; i < fields.length ; i ++) {
            //獲取屬性
            Field field = fields[i];
            //設定該屬性可訪問
            field.setAccessible(true);
            //在屬性Map中找到該屬性對應表頭
            title[i] = exportFields.get(field.getName());
        }

        // 第一步，建立一個workbook，對應一個Excel檔案
        HSSFWorkbook workbook = new HSSFWorkbook();

        // 第二步，在workbook中新增一個sheet,對應Excel檔案中的sheet
        HSSFSheet sheet = workbook.createSheet(sheetName);

        // 第三步，在sheet中新增表頭第0行,注意老版本poi對Excel的行數列數有限制short
        HSSFRow row = sheet.createRow(0);

        // 第四步，建立單元格，並設定值表頭 設定表頭居中
        HSSFCellStyle style = workbook.createCellStyle();
        style.setAlignment(HSSFCellStyle.ALIGN_CENTER); // 建立一個居中格式

        HSSFCell cell = null;

        //建立標題
        for(int i=0;i < title.length;i++){
            cell = row.createCell(i);
            cell.setCellValue(title[i]);
            cell.setCellStyle(style);
        }

        //建立內容
        for(int i = 0 ; i < list.size() ; i ++) {
            row = sheet.createRow(i + 1);
            for(int j = 0 ; j < fields.length ; j ++) {
                Field field = fields[j];
                field.setAccessible(true);
                String value = String.valueOf(field.get(list.get(0)));
                row.createCell(j).setCellValue(value);
            }
        }
        return workbook;
    }
}

測試類：

import com.taiji.jilin.common.entity.Activity;
import com.taiji.jilin.common.util.ExcelUtil;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.junit.Test;

import java.io.*;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

/**
 * @author 單繼重
 * @since 2017/11/23 13:58
*/

public class ExcelTest {

    @Test
    public void test () throws Exception {
        String fileName = "test.xls";
        String sheetName = "sheet1";

        List<Activity> activities = new ArrayList<Activity>();
        for (int i = 0 ; i < 10 ; i ++ ) {
            Activity activity = new Activity();
            activity.setName("名稱");
            activity.setContent("內容");
            activity.setCertificate("證書");
            activity.setIsFinish(1);
            activity.setBudget("預算");
            activity.setId(123);
            activity.setOrganization("組織");
            activity.setPopulation(123456);
            activity.setProvideHotel("是");
            activity.setProvideMeal("餐飲");
            activity.setQq("QQ");
            activity.setTel("電話");
            activity.setTime("時間");
            activity.setStatus("啊啊啊");
            activities.add(activity);
        }
        HSSFWorkbook hssfWorkbook = ExcelUtil.getHSSFWorkbook(sheetName,activities);
        File file = new File("F:\\Shanjz" + fileName);
        OutputStream outputStream = null;
        try {
            outputStream = new FileOutputStream(file);
            hssfWorkbook.write(outputStream);
            outputStream.flush();
            outputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}