解决调用ftpClient.retrieveFileStream(String remoteFilePath)第二次读取为空问题

public ResultData getFromFtpDataToDatabase(HttpServletRequest request){
        ResultData resultData = new ResultData(Result_Code.SUCCESS);
        String IP = Tools.processNull("***.***.***.***");
        //ftp端口是21 使用WinSCP 采用的是SSH连接端口号是22
        String PORT = Tools.processNull("21");
        String userName= Tools.processNull("userName");
        String passWord = Tools.processNull("passWord");
        String directory = Tools.processNull("");
        String upload = Tools.processNull("/upload/");
        String history = Tools.processNull("/history/");
        String filepath = "/test/";
        String paths = null;
        try {
            paths = new String(filepath.getBytes(),"UTF-8");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        //创建FTPClient对象
        FTPClient ftpClient = new FTPClient();
        try{
            //解决文件夹有中文是读不出文件问题
            ftpClient.setAutodetectUTF8(true);
            ftpClient.connect(IP, Integer.parseInt(PORT));
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
            ftpClient.setFileTransferMode(FTP.BLOCK_TRANSFER_MODE);
            ftpClient.login(userName, passWord);
            //读取文件夹下文件
            FTPFile[] files = ftpClient.listFiles(paths);
            //获取文件名称
            String saveAsFileName = null;
            for (int i = 0; i < files.length; i++) {
                saveAsFileName=files[i].getName();
                //文件路径
                String remoteFile = filepath+saveAsFileName;
                // get output stream of the response
                InputStream inputStream = ftpClient.retrieveFileStream(remoteFile);
                int available = inputStream.available();
                //将文件值转为二进制数据
                byte[] bytesArray = new byte[available];
                inputStream.read(bytesArray);
                //插入到数据库中,代码未体现
                inputStream.close();
                //ftpClient.getReply();
                //调用ftpClient.completePendingCommand()解决第二次读取为空情况
                ftpClient.completePendingCommand();

}
        }catch (IOException ex) {
            ex.printStackTrace();
        } finally {
            try {
                // 注销FTP客户端
                if(ftpClient!=null){
                    ftpClient.logout();
                }
            } catch (Exception e) {
                // 如果FTP注销失败什么也不做，忽略掉异常。
            }
            if (ftpClient.isConnected()) {
                try {
                    ftpClient.disconnect();
                } catch (IOException ex2) {
                    ex2.printStackTrace();
                }
            }
        }
        resultData.put("msg","操作成功");
        return resultData;
    }

调用ftpClient.completePendingCommand();
<strong>注意：</strong>FTP Server只有在接受到InputStream 执行close方法时，才会返回。所以一定先要执行close方法。不然在第一次下载一个文件成功之后，之后再次获取inputStream 就会返回null