导出到excle(三)（导出excel在项目中的应用）

package com.bjsxt.servlet;

import java.io.IOException;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.bjsxt.biz.DutyBiz;
import com.bjsxt.biz.impl.DutyBizImpl;
import com.bjsxt.dao.DutyDao;
import com.bjsxt.dao.impl.DutyDaoImpl;
import com.bjsxt.util.ExcelUtil;
@WebServlet("/login/exportDutyServlet")
public class ExportDutyServlet extends HttpServlet{
	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		DutyDao dd = new DutyDaoImpl();
		DutyBiz db = new DutyBizImpl();
		db.setDutyDao(dd);
		resp.setHeader("content-disposition", "attachment;filename=vv.xlsx");
		List<Map<String, String>> list = db.selectAll();
		ExcelUtil.export("考勤记录", resp.getOutputStream(), list, "username","name","dname","checkDate","checkIn","checkOut");
		resp.getOutputStream().flush();
	}
}

package com.bjsxt.util;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.List;
import java.util.Map;

import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.Font;
import org.apache.poi.ss.usermodel.HorizontalAlignment;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

import com.bjsxt.biz.DutyBiz;
import com.bjsxt.biz.impl.DutyBizImpl;
import com.bjsxt.dao.DutyDao;
import com.bjsxt.dao.impl.DutyDaoImpl;

public class ExcelUtil {
	public static void export(String sheetName,OutputStream os,List<?> list,String ... fields) {
		Workbook wb = new XSSFWorkbook();
		Sheet sheet = wb.createSheet(sheetName);
		//标题(创建一行)
		Row row = sheet.createRow(0);
		for (int i = 0; i < fields.length; i++) {
			//创建单元格（一行得第i列）
			Cell cell = row.createCell(i);
			//把标题放到单元格中。
			cell.setCellValue(fields[i]);
			
			//设置单元格格式
			CellStyle cs = wb.createCellStyle();
			//设置对齐方式/水平居中
			cs.setAlignment(HorizontalAlignment.CENTER);
			//设置字体
			Font font = wb.createFont();
			//加粗
			font.setBold(true);
			cs.setFont(font);
			//把样式应用到单元格中
			cell.setCellStyle(cs);
			
		}
		
		for(int i = 1;i<list.size();i++) {
			row = sheet.createRow(i);
			for(int j = 0;j<fields.length;j++) {
				Cell cell = row.createCell(j);
				@SuppressWarnings("unchecked")
				Map<String, String > map = (Map<String, String>) list.get(i);
				cell.setCellValue(map.get(fields[j])==null?"":map.get(fields[j]));
			}
		}
		try {
			wb.write(os);
		} catch (IOException e1) {
			e1.printStackTrace();
		}
		try {
			os.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		try {
			wb.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	public static void main(String[] args) throws Exception {
		DutyDao dd = new DutyDaoImpl();
		DutyBiz db = new DutyBizImpl();
		db.setDutyDao(dd);
		List<Map<String, String>> list = db.selectAll();
		OutputStream os = new FileOutputStream(new File("C:\\Users\\Windows\\Desktop\\dd.xlsx"));
		
		export("duty", os, list, "username","name","dname","checkDate","checkIn","checkOut");
	System.out.println("ok");
	}
	private static Object getFieldValue() {
		System.out.println("我的是从list中的map中取得数据，如果list中存放得是对象数据，则需要"
				+ "编写此方法将数据转化");
		return null;
	}
}