Apache-Commons：使用 CopyStreamEvent 时出现 CopyStreamException：IOException

Question

我正在尝试使用 apache-commons' FTPClient 类将文件上传到 FTP 服务器。 storeFile() 工作时没有错误，但我不想使用它，而是想创建一个监听器，这样我就可以关注上传进度。

当我运行代码时，它会愉快地连接并调用 uploadFile() - 这又会抛出 CopyStreamException: IOException。

我不擅长确定导致异常抛出的原因，这可能是我的“侦听器”对象吗？

这就是我的做法：

/** Upload a file to the server */
public boolean uploadFile (String localFile, String serverFile, CopyStreamAdapter listener ) throws IOException, FTPConnectionClosedException
{
    /*
    FileInputStream in = new FileInputStream(localFile);
    boolean result = storeFile(serverFile, in);
    in.close();
    return result;
    */

    InputStream stO = new BufferedInputStream( this.retrieveFileStream(serverFile), this.getBufferSize());
    OutputStream stD = new FileOutputStream(localFile);

    org.apache.commons.net.io.Util.copyStream(stO, stD, this.getBufferSize(), org.apache.commons.net.io.CopyStreamEvent.UNKNOWN_STREAM_SIZE, listener );
    this.completePendingCommand();

    // if we get this far, it's rainbows all the way down!
    return true ;
}

监听器：

CopyStreamAdapter listener = new org.apache.commons.net.io.CopyStreamAdapter()
{
    public void bytesTransferred (long totalBytesTransferred, int bytesTransferred, long streamSize)
    {
        // show progress
        System.out.println( "Upload progress: " + bytesTransferred + " of " + totalBytesTransferred ) ;
    }
} ;

f = new ftpClientWrapper() ;   // my class instance.
f.uploadFile(filename, "/public/dropfolder/test/testfile.test" , listener ) ;  // i've validated filename and uploadpath

编辑：这是堆栈跟踪：

Error on FTP upload: org.apache.commons.net.io.CopyStreamException: IOException caught while copying.
org.apache.commons.net.io.CopyStreamException: IOException caught while copying.
    at org.apache.commons.net.io.Util.copyStream(Util.java:129)
    at org.apache.commons.net.io.Util.copyStream(Util.java:173)
    at dk.capsize.ftpapp.ftpClientWrapper.uploadFile(JakartaFtpWrapper.java:105)
    at FTPApp.main(FTPApp.java:63)

提前致谢！