Question

我编写了这个类（来自示例）来下载远程FTP文件夹中包含的所有文件的标题。它运行良好，但当它下载文件＃146时，它会停止并显示NullPointException。文件＃146存在，我可以将其作为单个文件下载。

在方法remotePathLong中包含所有远程文件夹，这些文件夹写在一行中并与空格字符间隔开。

public void downloadHeader(String remotePathLong, String destPath, int bytes) {

    String remotePath;
    FTPFile[] fileList;
    String[] fileNameList;

    FTPClient ftpClient = new FTPClient();
    try {
        ftpClient.connect(server);
        ftpClient.login(user, pass);
        ftpClient.enterLocalPassiveMode();
        ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

        int indice = 0;
        int iP = 1;
        File downloadFile;
        String destFile;
        String remoteFile;
        byte[] bytesArray;
        int bytesRead = -1;
        while ((remotePath = getPath(remotePathLong, iP)) != null) {
            System.out.println("Loading file list from the server.....");
            fileNameList = ftpClient.listNames(remotePath);
            for (String file : fileNameList) {
                indice += 1;
                System.out.println(indice + " - Downloading: " + file);

                //Select files
                destFile = destPath.concat(file);

                downloadFile = new File(destFile);
                outputStream = new BufferedOutputStream(new FileOutputStream(downloadFile));

                //Download remote file (from ftp)
                remoteFile = remotePath.concat(file);

                inputStream = ftpClient.retrieveFileStream(remoteFile);
                bytesArray = new byte[bytes];
                bytesRead = inputStream.read(bytesArray);
                outputStream.write(bytesArray);

                //Save into file

                outputStream.close();
                inputStream.close();
                iP += 1;
            }
        }

    } catch (IOException ex) {
    } final{
        try {
            if (ftpClient.isConnected()) {
                ftpClient.logout();
                ftpClient.disconnect();
            }
        }
        catch (IOException ex1) {
            System.out.println("Error: " + ex1.getMessage());
        }
}

当它到达bytesRead = inputStream.read（bytesArray）时，在迭代＃146它给出了错误。但是如果在同一次迭代中我重新初始化连接它的工作原理。有人有建议吗？

Answer 1

由于网络流量或文件大小恰好是第146位，您的连接可能会超时。您可以打印第146个文件名并检查其大小。您还可以增加FTP连接超时时间

ftpClient.setControlKeepAliveTimeout(300); // set timeout to 5 minutes

FTP下载在文件＃146处停止

1 个答案: