閉關紀要：C# 結構化存儲在 Web 開發中的應用 (2)

FileSystem 基類架構與工廠模式實現

定義 Web 檔案系統抽象基類，包含共用邏輯 (GZip 傳輸、資料夾建立、快取標頭) 與工廠方法根據路由配置建立具體實現。

FileSystem.cs 基類完整代碼

using System;
using System.IO;
using System.Web;

namespace Step1.WebFileSystem {
    public class FileSystem {
        protected string path, physicsPath;
        protected Handler handle;
        protected HttpContext httpContext = null;
        protected Stream stream = null;

        public FileSystem(string path, Handler handle) {
            httpContext = HttpContext.Current;
            this.path = path;
            this.physicsPath = httpContext.Server.MapPath(path);
            this.handle = handle;
        }

        public virtual bool Exists() { return false; }
        public virtual DateTime GetLastWriteTime() { return DateTime.Now; }

        public virtual Stream GetWriter() {
            stream = httpContext.Response.OutputStream;
            if (this.handle.UseGzip) return new GZipOutputStream(stream);
            return stream;
        }

        public virtual Stream GetReader() { return null; }
        public virtual void TransmitFile() { return; }

        public virtual void Close() {
            if (stream != null) { stream.Close(); stream = null; }
        }

        public virtual void Dispose() { Close(); }

        public void TransmitStream(bool unZip) {
            Stream reader = unZip ? new GZipInputStream(this.GetReader()) : this.GetReader();
            byte[] buffer = new byte[1024];
            int p;
            while ((p = reader.Read(buffer, 0, 1024)) > 0) {
                httpContext.Response.OutputStream.Write(buffer, 0, p);
                httpContext.Response.Flush();
            }
            this.Close();
        }

        public void ResponseFile() {
            HttpRequest request = httpContext.Request;
            string acceptEncoding = request.Headers["Accept-Encoding"];
            if (this.handle.UseGzip && acceptEncoding != null && acceptEncoding.IndexOf("gzip") >= 0) {
                httpContext.Response.AddHeader("Content-Encoding", "gzip");
                this.TransmitFile();
            } else {
                if (this.handle.UseGzip) this.TransmitStream(true);
                else this.TransmitFile();
            }
        }

        protected void CreateFolder(string path, bool createCurrent) {
            string folder = Path.GetDirectoryName(path);
            if (!Directory.Exists(folder)) CreateFolder(folder, true);
            if (createCurrent) Directory.CreateDirectory(path);
        }

        public static FileSystem Create(string path) {
            Configuration config = Configuration.Instance();
            if (config != null) {
                for (int i = 0; i < config.handlers.Length; i++) {
                    if (config.handlers[i].UrlRegex.IsMatch(path)) {
                        switch (config.handlers[i].HandlerType) {
                            case "FFS": return new FileSystemFFS(path, config.handlers[i]);
                            case "OS": return new FileSystemOS(path, config.handlers[i]);
                            default: return new FileSystem(path, config.handlers[i]);
                        }
                    }
                }
            }
            return new FileSystem(path, new Handler());
        }
    }
}

架構亮點：

• 模板方法模式：ResponseFile 定義傳輸流程，子類實現具體存取
• 工廠方法：Create 根據正則路由動態建立 FFS/OS/基類實例
• GZip 透明支援：基類統一處理壓縮/解壓與 HTTP 標頭
• 資源管理：Close/Dispose 模式確保串流釋放