Question

我使用org.apache.commons.net.ftp.FtpClient创建了一个可靠的FTP类，可以并行下载多个文件，并在失败时重试。

奇怪的是，我似乎无法让代码识别失败。例如，如果我在传输过程中拉出以太网电缆，代码似乎就会继续阻塞：

client.retrieveFile(nextFile, ftpOutputStream);

线。有人可以告诉我它为什么阻止这一行而不是返回false或抛出异常？我错过了设置超时或类似的东西吗？

try {
    OutputStream ftpOutputStream = new FileOutputStream(fileName);

    System.out.println("Attempting to retrieve file [" + nextFile + "].");
    success = iclient.retrieveFile(nextFile, ftpOutputStream);
    System.out.println("Returned from retrieving file [" + nextFile + "].");

    ftpOutputStream.close();
}

//Can fail due to FTPConnectionClosedException, CopyStreamException, or IOException.  In any case, best course
//of action is to simply create a new connection, log in again, and change back to target directory.
catch(Exception ex) {

    try {
        System.out.println("Error occurred during download, deleting file and restarting.");
        Thread.sleep(1000);

        //Delete the failed file assuming any of it got written to the local drive.
        File f = new File(fileName);                        
        if(f.exists()) {
            System.out.println("Deleting file...");
            f.delete();
        }             

        Thread.sleep(5000);
    }
    catch (InterruptedException iex) {
        System.out.println("Interrupted exceptoin while respoding to failed FTP attempt.");
    }
}

Answer 1

“解决这个问题的方法是实现自己的SocketFactory并使用SocketClient.setSocketFactory设置它（FTPClient是SocketClient的子类）。当你实现SocketFactory时，添加一个setConnectTimeout方法或类似的东西。在createSocket方法里面，使用J2SE 1.4 connect方法和超时。“

请参阅“如何设置连接超时？”关于Commons Net FAQ的问题为什么会这样。

在Java中使用FTP并检测断开连接

1 个答案: