学步园

     1.引言

          实现一个FTP 文件的下载功能。

     2.初步构想

               a)采用类库的方式实现FTP 文件的下载，在界面层实现类库的调用。

               b)在文件下载的开始或结束能够反馈当前下载文件名、下载文件大小以及下载文件耗时等信息。

               c)在文件下载的过程中能够实现文件下载进度显示功能。

     3.FTP 类库实现

               第一步：创建工程

                    创建命名为LibDldFile类库工程。

                第二步：

                    在工程中建立IDldFile.cs 接口文件和FtpDldFile.cs 文件

                    定义文件下载接口

interface IDldFile
    {
        /// <summary>
        /// 下载文件列表
        /// </summary>
        List<string> DldFilePathList { get;set;}

        /// <summary>
        /// 下载文件
        /// </summary>
        /// <returns></returns>
        void Download();
    }

          第三步：初步实现FTP 下载功能

               下面的FTPDldFile 类能够初步实现FTP 文件的下载。

public class FtpDldFile : IDldFile
    {
        private string _ftpLoginUser = string.Empty;
        private string _ftpLoginPwd = string.Empty;
        private string _dldFileSaveDir = string.Empty;
        private List<string> _dldFileList = null;
        private UInt32 _ftpDldSize = 1024;

        /// <summary>
        /// 创建FTP 下载对象(文件保存路径默认为当前程序启动路径)
        /// </summary>
        /// <param name="dldFileList">下载文件路径列表</param>
        /// <param name="ftpLoginUser">FTP 登录用户</param>
        /// <param name="ftpLoginPwd">FTP 登录密码</param>
        public FtpDldFile(List<string> dldFileList, string ftpLoginUser, string ftpLoginPwd)
        {
            _dldFileList = dldFileList;
            _ftpLoginPwd = ftpLoginPwd;
            _ftpLoginUser = ftpLoginUser;
        }

        /// <summary>
        /// 创建FTP 下载对象
        /// </summary>
        /// <param name="dldFileList">下载文件路径列表</param>
        /// <param name="ftpLoginUser">FTP 登录用户</param>
        /// <param name="ftpLoginPwd">FTP 登录密码</param>
        /// <param name="dldFileSaveDir">下载文件保存路径</param>
        public FtpDldFile(List<string> dldFileList, string ftpLoginUser, string ftpLoginPwd, string dldFileSaveDir)
        {
            _dldFileList = dldFileList;
            _ftpLoginPwd = ftpLoginPwd;
            _ftpLoginUser = ftpLoginUser;
            _dldFileSaveDir = dldFileSaveDir;
        }

        /// <summary>
        /// 下载文件保存路径
        /// </summary>
        public string DldFileSaveDir
        {
            get
            {
                if (_dldFileSaveDir == string.Empty)
                    _dldFileSaveDir = AppDomain.CurrentDomain.BaseDirectory;

                //确保最后位为\
                if (_dldFileSaveDir.Substring(_dldFileSaveDir.Length - 1) != @"\")
                    _dldFileSaveDir += "\\";

                return _dldFileSaveDir;
            }
            set
            {
                _dldFileSaveDir = value;
            }
        }

        /// <summary>
        /// FTP 登录用户
        /// </summary>
        public string FtpLoginUser
        {
            get
            {
                if (_ftpLoginUser == string.Empty)
                    throw new Exception("The Ftp LoginUser is null");

                return _ftpLoginUser;
            }
            set
            {
                _ftpLoginUser = value;
            }
        }

        /// <summary>
        /// FTP 登录密码
        /// </summary>
        public string FtpLoginPwd
        {
            get
            {
                if (_ftpLoginPwd == string.Empty)
                    throw new Exception("The Ftp LoginPwd is null");

                return _ftpLoginPwd;
            }
            set
            {
                _ftpLoginPwd = value;
            }
        }

        /// <summary>
        /// 下载FTP 文件每次读取大小
        /// </summary>
        public UInt32 FtpDldSize
        {
            get
            {
                return _ftpDldSize;
            }
            set
            {
                _ftpDldSize = value;
            }
        }

        #region IDldFile 成员

        public List<string> DldFilePathList
        {
            get
            {
                if (_dldFileList == null)
                    _dldFileList = new List<string>();

                return _dldFileList;
            }
            set
            {
                _dldFileList = value;
            }
        }

        /// <summary>
        /// 将指定的FTP 路径中目录路径和文件名称分离，获取文件名称
        /// </summary>
        /// <param name="ftpPath"></param>
        /// <returns></returns>
        public static string ConvertPathToFileName(string ftpPath)
        {
            string[] strArray = ftpPath.Split(new char[] { '/' });
            return strArray[strArray.Length - 1];
        }

        public void Download()
        {
            //_dldFileList = new List<string>();
            //_dldFileList.Add(@"ftp://192.168.0.21/incoming/1.txt");
            //_ftpLoginPwd = "IECAS12345678";
            //_ftpLoginUser = "xiangwei";

            string curFileName = string.Empty;
            try
            {
                FtpWebRequest request;
                FtpWebResponse response;

                foreach (string strFile in DldFilePathList)
                {
                    curFileName = ConvertPathToFileName(strFile);

                    //校验文件是否存在，如果存在给出提示用户是否覆盖
                    if (System.IO.File.Exists(DldFileSaveDir + curFileName))
                    {
                        //通过委托获取用户是否同意覆盖
                        if (!EIsReplace(strFile))
                        {
                            continue;
                        }
                    }
                    
                    request = (FtpWebRequest)WebRequest.Create(strFile);
                    request.KeepAlive = false;
                    request.Credentials = new NetworkCredential(_ftpLoginUser, _ftpLoginPwd);

                    using (response = (FtpWebResponse)request.GetResponse())
                    {
                        Stream data = response.GetResponseStream();

                        //文件大小
                        long fileLength = response.ContentLength;

                        //文件输出路径
                        string targetPath = DldFileSaveDir + curFileName;

                        //每次下载文件大小
                        byte[] byteBuffer = new byte[_ftpDldSize];

                        //当前已下载文件大小
                        long currentDldBytes = 0;
                        //当前已下载文件百分比
                        double currentPercentage = 0;

                        using (FileStream output = new FileStream(targetPath, FileMode.OpenOrCreate))
                        {
                            int bytesRead = 0;
                            do
                            {
                                //上报下载文件百分比

                                bytesRead = data.Read(byteBuffer, 0, byteBuffer.Length);
                                if (bytesRead > 0)
                                {
                                    output.Write(byteBuffer, 0, bytesRead);
                                }

                                currentDldBytes += bytesRead;

                                currentPercentage = ((double)currentDldBytes / (double)fileLength) * 100;
                            }
                            while (bytesRead > 0);
                        }
                    }
                }
            }
            catch (WebException e)
            {
                throw new WebException("Download " + curFileName + " error has occored!The exception message is " + e.Message);
            }
        }

        #endregion
    }

 

          第四步：

               实现下载文件过程中信息反馈(包括下载文件信息、时间和百分比)

               首先，在接口中定义事件和委托：

/// <summary>
    /// 委托，用于标识提示用户是否需要覆盖当前文件
    /// </summary>
    /// <param name="fileName">覆盖文件名称</param>
    /// <returns></returns>
    public delegate bool DelegateIsReplace(string fileName);

    /// <summary>
    /// 委托，用于标识当前文件下载百分比
    /// </summary>
    /// <param name="dldPercentage">当前文件下载百分比</param>
    public delegate void DelegateDldPercentage(double dldPercentage);

    /// <summary>
    /// 委托，用于标识下载文件信息
    /// </summary>
    /// <param name="message"></param>
    public delegate void DelegateDldMessage(string message);

    interface IDldFile
    {
        List<string> DldFilePathList { get;set;}
        
        /// <summary>
        /// 下载文件
        /// </summary>
        /// <returns></returns>
        void Download();
        
        /// <summary>
        /// 事件，用于提示用户是否覆盖已经存在文件
        /// </summary>
        event DelegateIsReplace EIsReplace;

        /// <summary>
        /// 当前下载文件百分比
        /// </summary>
        event DelegateDldPercentage EDldPercentage;

        /// <summary>
        /// 下载文件信息
        /// </summary>
        event DelegateDldMessage EDldMessage;
    }

     原来的下载类再次实现该接口信息后，并且在下载Download 方法中调用事件：

public void Download()
        {
            //_dldFileList = new List<string>();
            //_dldFileList.Add(@"ftp://192.168.0.21/incoming/1.txt");
            //_ftpLoginPwd = "IECAS12345678";
            //_ftpLoginUser = "xiangwei";

            string curFileName = string.Empty;
            try
            {
                FtpWebRequest request;
                FtpWebResponse response;

                foreach (string strFile in DldFilePathList)
                {
                    curFileName = ConvertPathToFileName(strFile);

                    //校验文件是否存在，如果存在给出提示用户是否覆盖
                    if (System.IO.File.Exists(DldFileSaveDir + curFileName))
                    {
                        //通过委托获取用户是否同意覆盖
                        if (!EIsReplace(strFile))
                        {
                            continue;
                        }
                    }
                    
                    request = (FtpWebRequest)WebRequest.Create(strFile);
                    request.KeepAlive = false;
                    request.Credentials = new NetworkCredential(_ftpLoginUser, _ftpLoginPwd);

                    using (response = (FtpWebResponse)request.GetResponse())
                    {
                        Stream data = response.GetResponseStream();

                        //文件大小
                        long fileLength = response.ContentLength;

                        //文件输出路径
                        string targetPath = DldFileSaveDir + curFileName;

                        //每次下载文件大小
                        byte[] byteBuffer = new byte[_ftpDldSize];

                        //当前已下载文件大小
                        long currentDldBytes = 0;
                        //当前已下载文件百分比
                        double currentPercentage = 0;

                        //开始下载文件时间
                        DateTime startTime = DateTime.Now;
                        TimeSpan timeSpan;
                        using (FileStream output = new FileStream(targetPath, FileMode.OpenOrCreate))
                        {
                            int bytesRead = 0;

                            //上报开始下载文件信息
                            EDldMessage("开始下载文件：" + curFileName + " 文件大小：" + fileLength );
                            do
                            {
                                //上报下载文件百分比
                                EDldPercentage(currentPercentage);

                                bytesRead = data.Read(byteBuffer, 0, byteBuffer.Length);
                                if (bytesRead > 0)
                                {
                                    output.Write(byteBuffer, 0, bytesRead);
                                }

                                currentDldBytes += bytesRead;

                                currentPercentage = ((double)currentDldBytes / (double)fileLength) * 100;
                            }
                            while (bytesRead > 0);

                            timeSpan = DateTime.Now - startTime;
                            EDldMessage("下载" + curFileName + "完成，耗时：" + timeSpan.Minutes.ToString() + " 分 " + timeSpan.Seconds + " 秒 " + timeSpan.Milliseconds + "毫秒");
                        }
                    }
                }
            }
            catch (WebException e)
            {
                throw new WebException("Download " + curFileName + " error has occored!The exception message is " + e.Message);
            }
        }

           第五步：实现界面层       

               好了，一个简单的FTP 下载类库已经编写好了，我们再来写一个界面层调用程序来实现这个类库的调用吧.

               （ 不知道是不是博客园的问题，我这边上传JPG或者GIF文件不能成功，本来想截个图的。）

               界面中包括保存文件路径和下载按钮，和反馈信息显示栏及进度条。

               调用类库代码： 

private void btnSure_Click(object sender, EventArgs e)
        {
            FtpDldFile ftpDldFile = new FtpDldFile(DldFileList, _ftpLoginUser, _ftpLoginPwd, this.textBox1.Text);

            ftpDldFile.EIsReplace += new DelegateIsReplace(ftpDldFile_EIsReplace);
            ftpDldFile.EDldMessage += new DelegateDldMessage(ftpDldFile_EDldMessage);
            ftpDldFile.EDldPercentage += new DelegateDldPercentage(ftpDldFile_EDldPercentage);

            this.btnSure.Enabled = false;
            this.btnClose.Enabled = false;
            ftpDldFile.Download();