java – org.apache.commons.net.ftp.FTPClient listFiles()的问题

org.apache.commons.net.ftp.FTPClient的listFiles()方法适用于127.0.0.1上的Filezilla服务器,但在公共FTP服务器(如belnet.be)的根目录下返回null.

在下面的链接上有一个相同的问题,但enterRemotePassiveMode()似乎没有帮助.
Apache Commons FTPClient.listFiles

这可能是列表解析的问题吗？如果是这样,怎么能解决这个问题呢？

编辑：这是一个目录缓存转储：

FileZilla目录缓存转储

转储1个缓存目录

Entry 1:
Path: /
Server: anonymous@ftp.belnet.be:21,type: 4096
Directory contains 7 items:
  lrw-r--r-- ftp ftp      D          28      2009-06-17   debian
  lrw-r--r-- ftp ftp      D          31      2009-06-17   debian-cd
  -rw-r--r-- ftp ftp                  0 2010-03-04 13:30  keepalive.txt
  drwxr-xr-x ftp ftp      D        4096 2010-02-18 14:22  mirror
  lrw-r--r-- ftp ftp      D           6      2009-06-17   mirrors
  drwxr-xr-x ftp ftp      D        4096      2009-06-23   packages
  lrw-r--r-- ftp ftp      D           1      2009-06-17   pub

这是我使用我所做的包装器的代码(在包装器内测试产生相同的结果)：

public static void main(String[] args) {        
    ftputils ftputils = new ftputils();
    String ftpURL = "ftp.belnet.be";
    Connection connection = ftputils.getFTPClientManager().getConnection( ftpURL );

    if( connection == null ){
        System.out.println( "Could not connect" );
        return; 
    }

    FTPClientManager manager = connection.getFptClientManager();
    FTPClient client = manager.getClient();

    try {
        client.enterRemotePassiveMode();
    } catch (IOException e) {
        // Todo Auto-generated catch block
        e.printstacktrace();
    }

    if( connection != null ){
        System.out.println( "Connected to FTP" );
        connection.login("Anonymous","Anonymous");
        if( connection.isLoggedIn() ){
            System.out.println( "Login successful" );
            LoggedInManager loggedin = connection.getLoggedInManager(); 
            System.out.println( loggedin );
            String[] fileList = loggedin.getFileList();

            System.out.println( loggedin.getWorkingDirectory() );

            if( fileList == null || fileList.length == 0 )
                System.out.println( "No files found" );
            else{
                for (String name : fileList ) {
                    System.out.println( name );
                }
            }

            connection.disconnect();

            if( connection.isdisconnected() )
                System.out.println( "disconnection successful" );
            else
                System.out.println( "Error disconnecting" );
        }else{
            System.out.println( "Unable to login" );
        }
    } else {
        System.out.println( "Could not connect" );
    }
}

生成此输出：

Connected to FTP
Login succesful
utils.ftp.FTPClientManager$Connection$LoggedInManager@156ee8e
null
No files found
disconnection successful

在包装器内部(尝试使用listNames()和listFiles())：

public String[] getFileList() {
            String[] fileList = null;
            FTPFile[] ftpFiles = null;

            try {
                ftpFiles = client.listFiles();
                //fileList = client.listNames();
                //System.out.println( client.listNames() );
            } catch (IOException e) {
                return null;
            }

            fileList = new String[ ftpFiles.length ];

            for( int i = 0; i < ftpFiles.length; i++ ){
                fileList[ i ] = ftpFiles[ i ].getName();
            }

            return fileList;
        }

至于FTPClient,它按如下方式处理：

public class ftputils {

private FTPClientManager clientManager;

public FTPClientManager getFTPClientManager(){
    clientManager = new FTPClientManager();
    clientManager.setClient( new FTPClient() );

    return clientManager;
}

FTPClientConfig conf = new FTPClientConfig(FTPClientConfig.SYST_UNIX);

FTPClient client = FTPClient();
client.configure(conf);