java读取数据库保持到Excel

package org.zbq.service.impl;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.zbq.bean.User;
import org.zbq.dao.UserDAO;
import org.zbq.service.UserService;

public class UserServiceImpl implements UserService {
	private UserDAO dao;

	public UserDAO getDao() {
		return dao;
	}

	public void setDao(UserDAO dao) {
		this.dao = dao;
	}

	@Override
	public void doSaveUser(User user) {
		dao.doSaveUser(user);
	}

	@Override
	public void doDeleteUser(User user) {
		dao.doDeleteUser(user);
	}

	@Override
	public void doUpdateUser(User user) {
		dao.doUpdateUser(user);
	}

	@Override
	public User findUserById(Long id) {
		return dao.findUserById(id);
	}

	@Override
	public List<User> findAllUsers() {
		return dao.findAllUsers();
	}
	
	@Override
	public InputStream getInputStream(){
		HSSFWorkbook wb = new HSSFWorkbook();
		HSSFSheet sheet = wb.createSheet("sheet1");
		
		HSSFRow row = sheet.createRow(0);
		HSSFCell cell = row.createCell(0);
		cell.setCellValue("序号");
		
		cell = row.createCell(1);
		cell.setCellValue("姓");
		
		cell = row.createCell(2);
		cell.setCellValue("名");
		
		cell = row.createCell(3);
		cell.setCellValue("年龄");
		
		List<User> list = this.findAllUsers();
		for(int i=0; i<list.size(); i++){
			User user = list.get(i);
			row = sheet.createRow(i+1);
			
			cell = row.createCell(0);
			cell.setCellValue(i+1);
			
			cell = row.createCell(1);
			cell.setCellValue(user.getFirstName());
			
			cell = row.createCell(2);
			cell.setCellValue(user.getLastName());
			
			cell = row.createCell(3);
			cell.setCellValue(user.getAge());
		}
		
		ByteArrayOutputStream baos = new ByteArrayOutputStream();
		try {
			wb.write(baos);
		} catch (IOException e) {
			e.printStackTrace();
		}
		byte[] b = baos.toByteArray();
		InputStream is = new ByteArrayInputStream(b);
		return is;
	}
}