文件下载中文乱码

   String agent = (String)request.getHeader("USER-AGENT");  
          fileName = URLDecoder.decode(fileName, "UTF-8");
        if(agent != null && agent.indexOf("MSIE") == -1) {// FF
           fileName = "=?UTF-8?B?" + (new String(Base64.encodeBase64(fileName.getBytes("UTF-8")))) + "?=";    
        }else{
         this.fileName = URLEncoder.encode(fileName, "UTF-8");
        }