BlogEngine.NET 架構與原始碼分析系列 (13) 實作分析 (上)

HttpHandler 與 HttpModule 總覽

BlogEngine.NET 透過 web.config 註冊大量 HttpHandler 處理特定副檔名請求：

<httpHandlers>
  <add verb="*" path="file.axd" type="BlogEngine.Core.Web.HttpHandlers.FileHandler, BlogEngine.Core" />
  <add verb="*" path="image.axd" type="BlogEngine.Core.Web.HttpHandlers.ImageHandler, BlogEngine.Core" />
  <add verb="*" path="syndication.axd" type="BlogEngine.Core.Web.HttpHandlers.SyndicationHandler, BlogEngine.Core" />
  <add verb="*" path="sitemap.axd" type="BlogEngine.Core.Web.HttpHandlers.SiteMap, BlogEngine.Core" />
  <add verb="*" path="trackback.axd" type="BlogEngine.Core.Web.HttpHandlers.TrackbackHandler, BlogEngine.Core" />
  <add verb="*" path="pingback.axd" type="BlogEngine.Core.Web.HttpHandlers.PingbackHandler, BlogEngine.Core" />
  <add verb="*" path="opensearch.axd" type="BlogEngine.Core.Web.HttpHandlers.OpenSearchHandler, BlogEngine.Core" />
  <add verb="*" path="metaweblog.axd" type="BlogEngine.Core.API.MetaWeblog.MetaWeblogHandler, BlogEngine.Core" />
  <add verb="*" path="rsd.axd" type="BlogEngine.Core.Web.HttpHandlers.RsdHandler, BlogEngine.Core" />
  <add verb="*" path="css.axd" type="BlogEngine.Core.Web.HttpHandlers.CssHandler, BlogEngine.Core" />
  <add verb="*" path="js.axd" type="BlogEngine.Core.Web.HttpHandlers.JavaScriptHandler, BlogEngine.Core" />
  <add verb="*" path="rating.axd" type="BlogEngine.Core.Web.HttpHandlers.RatingHandler, BlogEngine.Core" />
  <add verb="*" path="opml.axd" type="BlogEngine.Core.Web.HttpHandlers.OpmlHandler, BlogEngine.Core" />
  <add verb="*" path="blogml.axd" type="BlogEngine.Core.Web.HttpHandlers.BlogMLExportHandler, BlogEngine.Core" />
  <add verb="*" path="sioc.axd" type="BlogEngine.Core.Web.HttpHandlers.Sioc, BlogEngine.Core" />
  <add verb="*" path="apml.axd" type="BlogEngine.Core.Web.HttpHandlers.Apml, BlogEngine.Core" />
  <add verb="*" path="foaf*.axd" type="BlogEngine.Core.Web.HttpHandlers.Foaf, BlogEngine.Core" />
</httpHandlers>

關鍵 Handler 功能

• FileHandler/ImageHandler：安全輸出附件/圖片，支援權限檢查與快取。
• SyndicationHandler：輸出 RSS/Atom Feed。
• Trackback/PingbackHandler：實作 Web 2.0 通知協定。
• OpenSearchHandler：產生 OpenSearch XML，瀏覽器搜尋列整合。
• MetaWeblogHandler：支援 Windows Live Writer 等離線寫作工具。
• CssHandler/JavaScriptHandler：合併、壓縮、快取靜態資源。

HttpModule

• ReferrerModule：記錄來源網址供統計。
• CompressionModule：GZIP/Deflate 壓縮回應。
• UrlRewriteModule：友善 URL 重寫。

總結

Handler/Module 機制讓 BlogEngine.NET 以零 ASPX 頁面實現豐富標準協定支援，展現 ASP.NET 管線擴充威力。