URLConnection FTP 列表文件

2022-01-09 00:00:00 file ftp java urlconnection 
URL url =  new URL("ftp://user:pass@ftp.example.com/thefolder/");
URLConnection connection = url.openConnection();
...
// List files in folder...

使用类似上面的方法，我想知道如何获取文件夹thefolder"中的文件列表?

Using something like the above, I was wondering how I could grab a list of files within folder 'thefolder'?

从这个原始问题开始，我整理了这个简单的 FTP 连接，它一切正常，看起来不错.它可以看到/live/conf/位置的所有文件，并将它们全部复制到本地/conf/位置.

Following on from this original question, I have put together this simple FTP connection which is all working and looking good. It can see all files in the /live/conf/ location and copies them all to the local /conf/ location.

唯一的问题是，它正在复制文件但没有内容.它们都是 0KB 并且是空的.

The only issue is, it is copying the files but there's no content.They are all 0KB and empty.

任何人都可以看到任何明显的复制文件名而不是文件内容的内容吗?

Can anyone see anything obvious that'd be copying the filename but not file content?

try {
    FTPClient ftp = new FTPClient();
    ftp.connect("000.000.000.000");
    ftp.login("USER", "PASSWORD");
    ftp.enterLocalPassiveMode();
    ftp.setFileType(FTP.BINARY_FILE_TYPE);

    FTPFile[] files = ftp.listFiles("/live/conf/");
    for (int i=0; i < files.length; i++) {
        if (files[i].getName().contains(".csv")) {

            String remoteFile1 = files[i].getName();
            File downloadFile1 = new File("/var/local/import/conf/"+files[i].getName());
            OutputStream outputStream1 = new BufferedOutputStream(new FileOutputStream(downloadFile1));
            ftp.retrieveFile(remoteFile1, outputStream1);
            outputStream1.close();                  

        }
    }
    ftp.disconnect();
} catch (SocketException ex) {
    ex.printStackTrace();
} catch (IOException ex) {
    ex.printStackTrace();
}

推荐答案

Java SE URLConnection 不适合从 FTP 主机检索文件列表的工作.至于 FTP，它基本上只支持 FTP 的 get 或 put 命令(检索或上传文件).它不支持您基本上正在寻找的 FTP ls 命令(列出文件)，更不用说其他许多命令了.

The Java SE URLConnection is insuitable for the job of retrieving a list of files from a FTP host. As to FTP, it basically only supports the FTP get or put commands (retrieve or upload file). It does not support the FTP ls command (list files) which you're basically looking for, let alone many others.

您需要寻找支持 FTP ls 命令(以及更多)的第 3 方库.一个常用的是 Apache Commons Net FtpClient.在其 javadoc 是演示了如何发出 ls:

You need to look for 3rd party libraries supporting the FTP ls command (and many more). A commonly used one is the Apache Commons Net FtpClient. In its javadoc is demonstrated how to issue a ls:

FTPClient f = new FTPClient();
f.connect(server);
f.login(username, password);
FTPFile[] files = f.listFiles(directory);

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