java如何使用POI导出Excel呢?

  1.定义 HSSFWorkbook 对象
  2.获取HSSFSheet 
  3.操作excel中的cell

HSSFWorkbook workbook = new HSSFWorkbook();//创建EXCEL文件
HSSFSheet sheet= workbook.createSheet("XXX"); //创建工作表
	//设置单元格宽度
 sheet.setDefaultColumnWidth(20);
 sheet.setColumnWidth(0, "班级名称".getBytes().length*2*256); //自适应宽度
 //设置单元格样式
 CellStyle boderStyle = workbook.createCellStyle(); // 垂直居中
 boderStyle.setVerticalAlignment(HSSFCellStyle.VERTICAL_CENTER);
 boderStyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
 //设置单元格字体
 HSSFFont font = workbook.createFont();  
 font.setFontName("等线");  
 font.setFontHeightInPoints((short) 12);  //字体大小
 boderStyle.setFont(font);
 
 //在sheet里创建第一行
 HSSFRow row=sheet.createRow(0);
 //创建单元格并设置单元格内容
 row.createCell(0).setCellValue("班级名称");
 row.createCell(1).setCellValue("姓名");
 row.createCell(2).setCellValue("成绩");
 row.createCell(3).setCellValue("数量");
 
 //获取排序后的班级
 list statisList = getProcuratorateName(beginDate, endDate);
 int count = 1;//计入班级的行
 for (StatisticsExcelVo stu : statisList) {
	 //数量小于零的不计入
	 if(!MatchUtil.isEmpty(stu) && stu.getCaseTotal() > 0){
		//班级名称
		HSSFRow row2=sheet.createRow(count);
		row2.createCell(0).setCellValue(stu.getCourtName());
		List userLoginNameList = new ArrayList<>();
		List statisUserList = new ArrayList<>();
		//合并班级名称单元格
		if(statisUserList.size() > 1){
			sheet.addMergedRegion(new CellRangeAddress(count,count+statisUserList.size()-1,0,0));    
		}
		int cellNum = 0; //计入用户的行
		for (StatisticsExcelVo string : statisUserList) {
			//赋值用户姓名等其他值,第一次时应该与当前的班级名称占用一行
			if(cellNum == 0){
				row2.createCell(1).setCellValue(string.getUserName());
				row2.createCell(2).setCellValue(string.getCaseTotal());
				row2.createCell(3).setCellValue(string.getJudgeTotal());
			}else{
				HSSFRow row3=sheet.createRow(count+cellNum);
				row3.createCell(1).setCellValue(string.getUserName());
				row3.createCell(2).setCellValue(string.getCaseTotal());
				row3.createCell(3).setCellValue(string.getJudgeTotal());
			}
			cellNum ++;
		}
		count = count+statisUserList.size();
	 }
}
//设置单元格样式
 for (int i = 0; i <= count; i++) {
	 HSSFRow row2 = sheet.getRow(i);
	 if (row2 != null) {
		 for (int j = 0; j <= 3; j++) {
			 HSSFCell cell_temp = row2.getCell(j);
			 if (cell_temp != null) {
			   cell_temp.setCellStyle(boderStyle);
			 }
		 }
	 }
  }
 //将文件输出
 OutputStream ouputStream = response.getOutputStream();
 response.reset();  
 String fileName = "xxx.xlsx";
 response.setHeader("Content-disposition", "attachment; filename="+new String(fileName.getBytes("utf-8"), "iso8859-1"));  
 response.setContentType("application/msexcel");   
 workbook.write(ouputStream);
 ouputStream.flush();
 ouputStream.close();