包装FTPWebRequest类

上篇文章讨论了C#从基于FTPS的FTP server下载数据 (FtpWebRequest 的使用)SSL 加密。不过细心的朋友应该可以发现FTPWebRequest 每次都是新生成一个request ( FTPWebRequest.create(uri) ), 这样对于一些复杂的需求，需要反复登陆，代码就会变得冗余啰嗦，那今天就和大家探讨一下如何包装FTPWebRequest类。如有好的想法或意见，希望各位大神老鸟多多指教。

 

先说一下我的需求：

 

去FTP Server 的一个指定路径下，找到更新时间最近的文件并下载。

那按照以上需求，就需要先去路径下，找到更新时间最近的文件，在根据文件名下载。 

 

这里封装一个FTPClient 类 （从网上找了一个FTPClient的壳子，忘记了原博客地址了，抱歉）

原理很简单，就是封装‘列出目录功能’和 ‘下载文件功能’。将用户名密码等放在FTPClient的属性中。

上码！

 

 using System.Collections.Generic;
 using System;
 using System.Net;
 using System.IO;
 using System.Security.Cryptography.X509Certificates;
 using System.Net.Security;

 namespace FtpClientBlogCase
 {

     #region "FTP client class"
     public class FTPclient
     {
         #region "CONSTRUCTORS"
         public FTPclient(string Hostname, string Username, string Password, bool EnableSSL)
         {
             this.Hostname = Hostname;
             this.Username = Username;
             this.Password = Password;
             this.EnableSsl = EnableSSL;
         }
         #endregion

         #region "Directory functions"
         public List<string> ListDirectory(string URI)
         {
             System.Net.FtpWebRequest ftp = GetRequest(URI);
             //Set request to do simple list
             ftp.Method = System.Net.WebRequestMethods.Ftp.ListDirectory;

             string str = GetStringResponse(ftp);
             //replace CRLF to CR, remove last instance
             str = str.Replace("\r\n", "\r").TrimEnd('\r');
             //split the string into a list
             List<string> result = new List<string>();
             result.AddRange(str.Split('\r'));
             return result;
         }
         #endregion

         #region "Download: File transfer FROM ftp server"
         /// <summary>
         /// Copy a file from FTP server to local
         /// </summary>
         /// <param name="sourceFilename">Target filename, if required</param>
         /// <param name="localFilename">Full path of the local file</param>
         /// <returns></returns>
         /// <remarks>
         /// Target can be blank (use same filename), or just a filename
         /// (assumes current directory) or a full path and filename
         /// 1.2 [HR] added CreateURI
         /// </remarks>
         public bool Download(string sourceFilename, string localFilename, bool PermitOverwrite)
         {
             //2. determine target file
             FileInfo fi = new FileInfo(localFilename);
             return this.Download(sourceFilename, fi, PermitOverwrite);
         }

         /// <summary>
         /// Version taking string/FileInfo
         /// </summary>
         /// <param name="sourceFilename"></param>
         /// <param name="targetFI"></param>
         /// <param name="PermitOverwrite"></param>
         /// <returns></returns>
         public bool Download(string sourceFilename, FileInfo targetFI, bool PermitOverwrite)
         {
             //1. check target
             if (targetFI.Exists && !(PermitOverwrite))
             {
                 throw (new ApplicationException("Target file already exists"));
             }

             //2. check source
             if (String.IsNullOrEmpty(sourceFilename))
             {
                 throw (new ApplicationException("File not specified"));
             }
             System.Net.FtpWebRequest ftp = GetRequest(sourceFilename);

             //Set request to download a file in binary mode
             ftp.Method = System.Net.WebRequestMethods.Ftp.DownloadFile;
             ftp.UseBinary = true;

             //open request and get response stream
             using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
             {
                 using (Stream responseStream = response.GetResponseStream())
                 {
                     //loop to read & write to file
                     responseStream.ReadTimeout = ;
                     using (FileStream fs = targetFI.OpenWrite())
                     {
                         try
                         {
                             byte[] buffer = new byte[**];
                             int read = ;
                             do
                             {
                                 read = responseStream.Read(buffer, , buffer.Length);
                                 fs.Write(buffer, , read);
                                 fs.Flush();
                             } while (read != );
                             responseStream.Close();
                             fs.Flush();
                             fs.Close();
                         }
                         catch (Exception)
                         {
                             //catch error and delete file only partially downloaded
                             fs.Close();
                             //delete target file as it's incomplete
                             targetFI.Delete();
                             throw;
                         }
                     }

                     responseStream.Close();
                 }

                 response.Close();
             }

             return true;
         }

         #endregion

         #region "private supporting fns"

         //Get the basic FtpWebRequest object with the
         //common settings and security
         private FtpWebRequest GetRequest(string URI)
         {
             //create request
             FtpWebRequest result = (FtpWebRequest)FtpWebRequest.Create(URI);
             //Set the login details
             result.Credentials = GetCredentials();
             // support for EnableSSL
             result.EnableSsl = EnableSsl;
             result.Timeout = ;

             ServicePoint sp = result.ServicePoint;
             ServicePointManager.ServerCertificateValidationCallback =
                 new RemoteCertificateValidationCallback(ValidateServerCertificate);

             return result;
         }

         /// <summary>
         /// Ensure chars in path are correctly escaped e.g. #
         /// </summary>
         /// <param name="path">path to escape</param>
         /// <returns></returns>
         private string GetEscapedPath(string path)
         {
             string[] parts;
             parts = path.Split('/');
             string result;
             result = "";
             foreach (string part in parts)
             {
                 if (!string.IsNullOrEmpty(part))
                     result += @"/" + Uri.EscapeDataString(part);
             }
             return result;
         }

         /// <summary>
         /// Get the credentials from username/password
         /// </summary>
         /// <remarks>
         /// Amended to store credentials on first use, for re-use
         /// when using KeepAlive=true
         /// </remarks>
         private System.Net.ICredentials GetCredentials()
         {
             if (_credentials == null)
                 _credentials = new System.Net.NetworkCredential(Username, Password);
             return _credentials;
         }

         /// <summary>
         /// stored credentials
         /// </summary>
         private System.Net.NetworkCredential _credentials = null;

         /// <summary>
         /// Obtains a response stream as a string
         /// </summary>
         /// <param name="ftp">current FTP request</param>
         /// <returns>String containing response</returns>
         /// <remarks>
         /// FTP servers typically return strings with CR and
         /// not CRLF. Use respons.Replace(vbCR, vbCRLF) to convert
         /// to an MSDOS string
         /// 1.1: modified to ensure accepts UTF8 encoding
         /// </remarks>
         private string GetStringResponse(FtpWebRequest ftp)
         {
             //Get the result, streaming to a string
             string result = "";
             using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
             {
                 long size = response.ContentLength;
                 using (Stream datastream = response.GetResponseStream())
                 {
                     using (StreamReader sr = new StreamReader(datastream, System.Text.Encoding.UTF8))
                     {
                         result = sr.ReadToEnd();
                         sr.Close();
                     }

                     datastream.Close();
                 }

                 response.Close();
             }

             return result;
         }

         /// <summary>
         /// Gets the size of an FTP request
         /// </summary>
         /// <param name="ftp"></param>
         /// <returns></returns>
         /// <remarks></remarks>
         private long GetSize(FtpWebRequest ftp)
         {
             long size;
             using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
             {
                 size = response.ContentLength;
                 response.Close();
             }

             return size;
         }

         private bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
         {
             return true;
         }

         #endregion

         #region Properties

         public string Hostname { get; set; }
         public string Username { get; set; }
         public string Password { get; set; }
         public bool EnableSsl { get; set; }

         #endregion

     }
     #endregion

 }

FTPClient.cs

 using System;
 using System.Configuration;
 using System.Linq;

 namespace FtpClientBlogCase
 {
     class Program
     {
         static void Main(string[] args)
         {
             DownloadFileFromFTP.DownloadFileFromNetwork();
             Console.WriteLine("Done");
         }
     }

     public class DownloadFileFromFTP
     {
         public static void DownloadFileFromNetwork()
         {
             var fullDataServer = "XXX";
             var userName = "XXX";
             var password = "XXX";
             var fc = new FTPclient(fullDataServer, userName, password, true);
             var list = fc.ListDirectory(fullDataServer);
             Console.WriteLine("The file is downloading, please wait...");
             fc.Download(fullDataServer + list.Last(), list.Last(), true);

         }
     }
 }

Program.cs

在类FTPClient中，private FtpWebRequest GetRequest(string URI) 是最重要的方法，它为每一个功能提供了一个FtpWebRequest对象，避免了每次生成request对象的冗余冗余代码。