POI实现excel导出功能

/**
 * Export工具类
 */
public void exportUtil (){
		//list为查询出的数据集合
		List list = new ArrayList();
		//导出excel文件的名字
		String filename = "文件名字";
//		/**
//		 * 获取response对象 获取HttpServletResponse response ;  
//		 */
		response.setContentType("application/octet-stream");
		response.setHeader("Content-Disposition", "attachment;filename="+new String(filename.getBytes("gbk"), "iso8859-1")+".xls");
		//创建Excel
		HSSFWorkbook wb = new HSSFWorkbook();
		//创建第一个sheet取名sheet0
		HSSFSheet sheet = wb.createSheet("sheet0");
		//表头名称
		String titles = "姓名,电话,QQ,邮箱,留言内容"; 
		//对应的数据库字段 (查询出的list)
		String fields = "name,phone,qq,email,content";
		ExportUtil.outputHeaders(titles.split(","), sheet);
		ExportUtil.outputColumns(fields.split(","), list, sheet, 1);
		//获取输出流，写入excel 并关闭
		ServletOutputStream out = response.getOutputStream();
		wb.write(out);
		out.flush();
		out.close();
	}

        /**
	 * 设置sheet表头信息
	 * @param titlesInfo 表头的String数组
	 * @param sheet
	 */
	public static void outputHeaders(String[] titlesInfo,HSSFSheet sheet ){
		HSSFRow row = sheet.createRow(0);
		for (int i = 0; i < titlesInfo.length; i++) {
			sheet.setColumnWidth(i, 4000);
			row.createCell(i).setCellValue(titlesInfo[i]);
		}
	}

       /**
	 * 循环插入数据
	 * @param headersInfo  表体的String数组
	 * @param columnsInfo  包含表体数据的list集合
	 * @param sheet
	 * @param rowIndex     从第几行开始插入数据
	 */
	 public static void outputColumns(String[] headersInfo,List columnsInfo,HSSFSheet sheet,int rowIndex ){
		HSSFRow row ;
		//循环插入多少行
		for (int i = 0; i < columnsInfo.size(); i++) {
			row = sheet.createRow(rowIndex+i);
			Object obj = columnsInfo.get(i);
			//循环每行多少列
			for (int j = 0; j < headersInfo.length; j++) {
				Object value = getFieldValueByName(headersInfo[j],obj);
				if(value == null){
					value="";
				}
				row.createCell(j).setCellValue(value.toString());
			}
		}	
	}

/**
	 * 根据对象的属性获取值
	 * @param string
	 * @param obj
	 * @return
	 */
	private static Object getFieldValueByName(String fieldName, Object obj) {
		String firstLetter = fieldName.substring(0,1).toUpperCase();
		String getter = "get" +firstLetter + fieldName.substring(1);
		try {
			Method method = obj.getClass().getMethod(getter, new Class[]{});
			Object value = method.invoke(obj, new Object[]{});
			return value;
		} catch (Exception e) {
			e.printStackTrace();
			logger.error("属性不存在！");
			return null;
		} 
	}