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！
1 using System.Collections.Generic;
2 using System;
3 using System.Net;
4 using System.IO;
5 using System.Security.Cryptography.X509Certificates;
6 using System.Net.Security;
7
8 namespace FtpClientBlogCase
9 {
10
11
12 #region "FTP client class"
13 public class FTPclient
14 {
15 #region "CONSTRUCTORS"
16 public FTPclient(string Hostname, string Username, string Password, bool EnableSSL)
17 {
18 this.Hostname = Hostname;
19 this.Username = Username;
20 this.Password = Password;
21 this.EnableSsl = EnableSSL;
22 }
23 #endregion
24
25 #region "Directory functions"
26 public List<string> ListDirectory(string URI)
27 {
28 System.Net.FtpWebRequest ftp = GetRequest(URI);
29 //Set request to do simple list
30 ftp.Method = System.Net.WebRequestMethods.Ftp.ListDirectory;
31
32 string str = GetStringResponse(ftp);
33 //replace CRLF to CR, remove last instance
34 str = str.Replace("\r\n", "\r").TrimEnd(‘\r‘);
35 //split the string into a list
36 List<string> result = new List<string>();
37 result.AddRange(str.Split(‘\r‘));
38 return result;
39 }
40 #endregion
41
42 #region "Download: File transfer FROM ftp server"
43 /// <summary>
44 /// Copy a file from FTP server to local
45 /// </summary>
46 /// <param name="sourceFilename">Target filename, if required</param>
47 /// <param name="localFilename">Full path of the local file</param>
48 /// <returns></returns>
49 /// <remarks>
50 /// Target can be blank (use same filename), or just a filename
51 /// (assumes current directory) or a full path and filename
52 /// 1.2 [HR] added CreateURI
53 /// </remarks>
54 public bool Download(string sourceFilename, string localFilename, bool PermitOverwrite)
55 {
56 //2. determine target file
57 FileInfo fi = new FileInfo(localFilename);
58 return this.Download(sourceFilename, fi, PermitOverwrite);
59 }
60
61 /// <summary>
62 /// Version taking string/FileInfo
63 /// </summary>
64 /// <param name="sourceFilename"></param>
65 /// <param name="targetFI"></param>
66 /// <param name="PermitOverwrite"></param>
67 /// <returns></returns>
68 public bool Download(string sourceFilename, FileInfo targetFI, bool PermitOverwrite)
69 {
70 //1. check target
71 if (targetFI.Exists && !(PermitOverwrite))
72 {
73 throw (new ApplicationException("Target file already exists"));
74 }
75
76 //2. check source
77 if (String.IsNullOrEmpty(sourceFilename))
78 {
79 throw (new ApplicationException("File not specified"));
80 }
81 System.Net.FtpWebRequest ftp = GetRequest(sourceFilename);
82
83 //Set request to download a file in binary mode
84 ftp.Method = System.Net.WebRequestMethods.Ftp.DownloadFile;
85 ftp.UseBinary = true;
86
87 //open request and get response stream
88 using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
89 {
90 using (Stream responseStream = response.GetResponseStream())
91 {
92 //loop to read & write to file
93 responseStream.ReadTimeout = 600000;
94 using (FileStream fs = targetFI.OpenWrite())
95 {
96 try
97 {
98 byte[] buffer = new byte[2048*1000*2];
99 int read = 0;
100 do
101 {
102 read = responseStream.Read(buffer, 0, buffer.Length);
103 fs.Write(buffer, 0, read);
104 fs.Flush();
105 } while (read != 0);
106 responseStream.Close();
107 fs.Flush();
108 fs.Close();
109 }
110 catch (Exception)
111 {
112 //catch error and delete file only partially downloaded
113 fs.Close();
114 //delete target file as it‘s incomplete
115 targetFI.Delete();
116 throw;
117 }
118 }
119
120 responseStream.Close();
121 }
122
123 response.Close();
124 }
125
126
127 return true;
128 }
129
130 #endregion
131
132 #region "private supporting fns"
133
134
135 //Get the basic FtpWebRequest object with the
136 //common settings and security
137 private FtpWebRequest GetRequest(string URI)
138 {
139 //create request
140 FtpWebRequest result = (FtpWebRequest)FtpWebRequest.Create(URI);
141 //Set the login details
142 result.Credentials = GetCredentials();
143 // support for EnableSSL
144 result.EnableSsl = EnableSsl;
145 result.Timeout = 600000;
146
147 ServicePoint sp = result.ServicePoint;
148 ServicePointManager.ServerCertificateValidationCallback =
149 new RemoteCertificateValidationCallback(ValidateServerCertificate);
150
151 return result;
152 }
153
154 /// <summary>
155 /// Ensure chars in path are correctly escaped e.g. #
156 /// </summary>
157 /// <param name="path">path to escape</param>
158 /// <returns></returns>
159 private string GetEscapedPath(string path)
160 {
161 string[] parts;
162 parts = path.Split(‘/‘);
163 string result;
164 result = "";
165 foreach (string part in parts)
166 {
167 if (!string.IsNullOrEmpty(part))
168 result += @"/" + Uri.EscapeDataString(part);
169 }
170 return result;
171 }
172
173
174 /// <summary>
175 /// Get the credentials from username/password
176 /// </summary>
177 /// <remarks>
178 /// Amended to store credentials on first use, for re-use
179 /// when using KeepAlive=true
180 /// </remarks>
181 private System.Net.ICredentials GetCredentials()
182 {
183 if (_credentials == null)
184 _credentials = new System.Net.NetworkCredential(Username, Password);
185 return _credentials;
186 }
187
188 /// <summary>
189 /// stored credentials
190 /// </summary>
191 private System.Net.NetworkCredential _credentials = null;
192
193
194
195 /// <summary>
196 /// Obtains a response stream as a string
197 /// </summary>
198 /// <param name="ftp">current FTP request</param>
199 /// <returns>String containing response</returns>
200 /// <remarks>
201 /// FTP servers typically return strings with CR and
202 /// not CRLF. Use respons.Replace(vbCR, vbCRLF) to convert
203 /// to an MSDOS string
204 /// 1.1: modified to ensure accepts UTF8 encoding
205 /// </remarks>
206 private string GetStringResponse(FtpWebRequest ftp)
207 {
208 //Get the result, streaming to a string
209 string result = "";
210 using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
211 {
212 long size = response.ContentLength;
213 using (Stream datastream = response.GetResponseStream())
214 {
215 using (StreamReader sr = new StreamReader(datastream, System.Text.Encoding.UTF8))
216 {
217 result = sr.ReadToEnd();
218 sr.Close();
219 }
220
221 datastream.Close();
222 }
223
224 response.Close();
225 }
226
227 return result;
228 }
229
230 /// <summary>
231 /// Gets the size of an FTP request
232 /// </summary>
233 /// <param name="ftp"></param>
234 /// <returns></returns>
235 /// <remarks></remarks>
236 private long GetSize(FtpWebRequest ftp)
237 {
238 long size;
239 using (FtpWebResponse response = (FtpWebResponse)ftp.GetResponse())
240 {
241 size = response.ContentLength;
242 response.Close();
243 }
244
245 return size;
246 }
247
248 private bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
249 {
250 return true;
251 }
252
253
254
255 #endregion
256
257 #region Properties
258
259 public string Hostname { get; set; }
260 public string Username { get; set; }
261 public string Password { get; set; }
262 public bool EnableSsl { get; set; }
263
264 #endregion
265
266 }
267 #endregion
268
269
270 }
FTPClient.cs
1 using System;
2 using System.Configuration;
3 using System.Linq;
4
5 namespace FtpClientBlogCase
6 {
7 class Program
8 {
9 static void Main(string[] args)
10 {
11 DownloadFileFromFTP.DownloadFileFromNetwork();
12 Console.WriteLine("Done");
13 }
14 }
15
16 public class DownloadFileFromFTP
17 {
18 public static void DownloadFileFromNetwork()
19 {
20 var fullDataServer = "XXX";
21 var userName = "XXX";
22 var password = "XXX";
23 var fc = new FTPclient(fullDataServer, userName, password, true);
24 var list = fc.ListDirectory(fullDataServer);
25 Console.WriteLine("The file is downloading, please wait...");
26 fc.Download(fullDataServer + list.Last(), list.Last(), true);
27
28 }
29 }
30 }
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。
时间： 2024-10-13 10:07:57