c# - 当命令在 .NET 中的 FTP 服务器上失败时会发生什么？

Question

我有这个源代码:

public static void FTP_SERVER()
{
    FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/");
    request.Method = WebRequestMethods.Ftp.ListDirectory;
    request.Credentials = new NetworkCredential("myusername", "mypassword");
    FtpWebResponse response = (FtpWebResponse)request.GetResponse();
    Stream responseStream = response.GetResponseStream();
    StreamReader reader = new StreamReader(responseStream);
    ArrayList directories = new ArrayList();
    while (!reader.EndOfStream)
    {
        String directory = reader.ReadLine();
        int i = 0;
        for (i = 0; i < directories.Count && Convert.ToInt32(directory) > Convert.ToInt32(directories[i] + ""); i++);
        directories.Insert(i, directory);
    }
    String[] agents = Crawler.CrawlerDbUtils.getAllAgentIDs();

    reader.Close();
    response.Close();
    int j = 0;
    for (int i = 0; i < directories.Count; i++)
    {
        try
        {
            while ((j < agents.Length) && (Convert.ToInt32(agents[j]) < Convert.ToInt32(directories[i] + "")))
            {
                try
                {
                    request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + agents[j]);
                    request.Method = WebRequestMethods.Ftp.MakeDirectory;
                    request.Credentials = new NetworkCredential("myusername", "mypassword");
                    response = (FtpWebResponse)request.GetResponse();
                    responseStream = response.GetResponseStream();
                    response.Close();
                }
                catch (Exception exception)
                { }
                j++;
            }
            if (Convert.ToInt32(agents[j]) == Convert.ToInt32(directories[i] + ""))
            {
                request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + directories[i] + "/");
                request.Method = WebRequestMethods.Ftp.ListDirectory;
                request.Credentials = new NetworkCredential("myusername", "mypassword");
                response = (FtpWebResponse)request.GetResponse();
                responseStream = response.GetResponseStream();
                reader = new StreamReader(responseStream);
                ArrayList files = new ArrayList();
                while (!reader.EndOfStream)
                {
                    String file = reader.ReadLine();
                    int q = 0;
                    for (q = 0; q < files.Count && file.CompareTo(files[q] + "") > 0; q++) ;
                    files.Insert(q, file);
                }
                reader.Close();
                response.Close();
                String[] dbFiles = Crawler.CrawlerDbUtils.getAllPictures(directories[i] + "");
                int r = 0;
                for (int q = 0; q < files.Count; q++)
                {
                    while ((r < dbFiles.Length) && ((dbFiles[r] + "").CompareTo(files[q] + "") < 0))
                    {
                        r++;
                    }
                    try
                    {
                        if ((r >= dbFiles.Length) || ((dbFiles[r] + "").Equals(files[q]) == false))
                        {
                            request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + directories[i] + "/" + files[q]);
                            request.Method = WebRequestMethods.Ftp.DeleteFile;
                            request.Credentials = new NetworkCredential("myusername", "mypassword");
                            response = (FtpWebResponse)request.GetResponse();
                            responseStream = response.GetResponseStream();
                            response.Close();
                        }
                    }
                    catch (Exception exception)
                    { }
                }
                j++;
            }
            else
            {
                request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + directories[i] + "/");
                request.Method = WebRequestMethods.Ftp.ListDirectory;
                request.Credentials = new NetworkCredential("myusername", "mypassword");
                response = (FtpWebResponse)request.GetResponse();
                responseStream = response.GetResponseStream();
                reader = new StreamReader(responseStream);
                ArrayList files = new ArrayList();
                while (!reader.EndOfStream)
                {
                    files.Add(reader.ReadLine());
                }
                reader.Close();
                response.Close();
                for (int k = 0; k < files.Count; k++)
                {
                    request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + directories[i] + "/" + files[k]);
                    request.Method = WebRequestMethods.Ftp.DeleteFile;
                    request.Credentials = new NetworkCredential("myusername", "mypassword");
                    response = (FtpWebResponse)request.GetResponse();
                    responseStream = response.GetResponseStream();
                    response.Close();
                }
                request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + directories[i] + "/");
                request.Method = WebRequestMethods.Ftp.RemoveDirectory;
                request.Credentials = new NetworkCredential("myusername", "mypassword");
                response = (FtpWebResponse)request.GetResponse();
                responseStream = response.GetResponseStream();
                response.Close();
            }
        }
        catch (Exception exception)
        {
        }
    }
    while (j < agents.Length)
    {
        try
        {
            request = (FtpWebRequest)WebRequest.Create("ftp://myurl.com/mainfolder/" + agents[j] + "/");
            request.Method = WebRequestMethods.Ftp.MakeDirectory;
            request.Credentials = new NetworkCredential("myusername", "mypassword");
            response = (FtpWebResponse)request.GetResponse();
            responseStream = response.GetResponseStream();
            response.Close();
        }
        catch (Exception exception)
        { }
        j++;
    }
    MessageBox.Show("DONE");

}

它用于从服务器中删除不推荐使用的目录和文件。我有一个主文件夹，其中所有子文件夹都是数字，所有子文件夹只包含文件(没有子文件夹的子文件夹)

服务器上的文件夹将存储在一个称为目录的 ArrayList 中。

存储在数据库中的目录 ID 将被加载到称为代理的 String[] 中。

目录会按升序排列，同理，agent也会按升序排列(本项目都是数字，所以按数字排序)

如果一个目录在服务器上存在，但在数据库中不存在，则将其删除(先删除其所有文件，然后再删除文件夹本身)

如果一个目录在服务器上不存在，但存在于存储的目录列表中，则将在服务器上创建它。

如果一个目录存在于服务器上并且也在存储的目录列表中，则不推荐使用的文件将被删除。服务器上相应目录下的文件称为files，而数据库中存储的文件则存储在一个名为dbFiles的String[]中。

这个函数本质上就是创建要创建的文件夹，删除要删除的文件夹，删除要删除的文件，就可以了。但是，我注意到在某些情况下，当发生服务器错误时，索引会下降，我想知道可能是什么原因。

例如 i = 500 并且(我不知道为什么)当 i = 100 时，命令会捕获到服务器错误并且 i 降回 100。

我的问题是:为什么我的索引会在捕获到之前发生的错误时回落？

j 会回到 i 100 岁时的状态吗？

如何防止这种回退？

Answer 1

你应该重构你的代码，使 ftp 命令在函数中，而不是到处复制/粘贴这些 ftp 命令，你有一些像这样的流程:

String[] directories = ftpGetListing("ftp://myurl.com/mainfolder/");
String[] agents = Crawler.CrawlerDbUtils.getAllAgentIDs();

String[] combinedDirectories = getElementsInBothArray(directories, agents);
String[] serverOnlyDirectories = getElementsOnlyInFirstArray(directories, agents);
String[] agentOnlyDirectories = getElementsOnlyInFirstArray(agents, directories);

// step 1: delete all server only directories
ftpDeleteDirectories("ftp://myurl.com/mainfolder/", serverOnlyDirectories);

// step 2: create all agent only directories
ftpCreateDirectories("ftp://myurl.com/mainfolder/", agentOnlyDirectories);

// step 3: depricate all files
foreach(String dir in combinedDirectories)
{
  String ftpDir = "ftp://myurl.com/mainfolder/" + dir + "/";
  String[] serverFiles = ftpGetListing(ftpDir);
  String[] agentFiles = Crawler.CrawlerDbUtils.getAllPictures(dir);

  String[] serverOnlyFiles = getElementsOnlyInFirstArray(serverFiles, agentFiles);

  foreach(String file in serverOnlyFiles)
  {
    ftpDeleteFile(ftpDir + file);
  }
}

然后您只需为 ftpGetListing、ftpDeleteDirectories、ftpCreateDirectories 和 ftpDeleteFile 实现非常简单的功能。哦，是的，还有一些简单的数组操作函数，例如:getElementsInBothArrays 和 getElementsOnlyInFitstArray。