读取数据库文件用POI生成Excel

读取数据库中的数据导出成Excel在页面可供用户下载，代码如下：

/**
	 * 读取数据库文件生成Excel
	 * 
	 */
	public String paymentsToExcel(List<VerifyCode> verifyCodesList) {
     //verifyCodesList是读取数据库数据存入List中
		String sheetName = "随机码列表"; 
		String xlsName = System.currentTimeMillis()+".xls";
		//创建Excel的工作册 Workbook,对应到一个excel文档
		HSSFWorkbook workbook = new HSSFWorkbook();
		//创建Excel的工作sheet,对应到一个excel文档的tab
		HSSFSheet sheet = workbook.createSheet();
		workbook.setSheetName(0,sheetName);
		HSSFRow row= sheet.createRow((short)0);;
		HSSFCell cell;
		int nColumn=fields.length;
		//excel列名
		row = sheet.createRow((short)0);
		for(int j=1;j<=nColumn;j++)
		{
			//序列ID
			cell = row.createCell(j-1);
			cell.setCellType(HSSFCell.CELL_TYPE_STRING);
			Object objReturnValue = fieldsName[j-1] ;
			cell.setCellValue(objReturnValue+"");
		}
		int iRow=1;
		//写入各条记录，每条记录对应Excel中的一行
		for (LicaiVerifyCode liCaiVerifyCode:verifyCodesList){
			row = sheet.createRow((short)iRow);
			for(int j=1;j<=nColumn;j++)
			{
				//序列ID
				cell = row.createCell(j-1);
				String objReturnValue = "" ;
				cell.setCellType(HSSFCell.CELL_TYPE_STRING);
				try {
					Method currentMethod = liCaiVerifyCode.getClass().getMethod(fields[j-1]);
					if(fields[j-1].equals("getEffectiveTime")||fields[j-1].equals("getFailureTime")||fields[j-1].equals("getCreateTime")||fields[j-1].equals("getLastModifyTime")){
						SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd hh-mm-ss");
						objReturnValue = sd.format(currentMethod.invoke(liCaiVerifyCode));
					}else{
						objReturnValue = String.valueOf(currentMethod.invoke(liCaiVerifyCode));
					}
				} catch (Exception ex) {
					ex.printStackTrace();	
				}
				cell.setCellValue(objReturnValue+"");
			}
			iRow++;
		}
		try {
			//输出
			ActionContext context = ActionContext.getContext();
			HttpServletResponse response = (HttpServletResponse) context.get(ServletActionContext.HTTP_RESPONSE); 
			response.setHeader("Content-disposition",  "attachment;  filename="+xlsName);//设定输出文件头
			response.setContentType("application/vnd.ms-excel");//定义输出类型
			OutputStream os = response.getOutputStream();
			workbook.write(os); 
			os.close();
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		return SUCCESS;
	}