//不支持Session internal class SyncAjaxHandler : IHttpHandler { private Page _page; private CacheMethodInfo _cacheMethodInfo; internal SyncAjaxHandler(Page page, CacheMethodInfo cacheMethodInfo) { _page = page; _cacheMethodInfo = cacheMethodInfo; } public void ProcessRequest(HttpContext context) { //执行方法（下面详细介绍） Executor.Execute(_page, context, _cacheMethodInfo); } public bool IsReusable { get { return false; } } public static SyncAjaxHandler CreateHandler(Page page, CacheMethodInfo cacheMethodInfo, SessionState state) { switch (state) { case SessionState.ReadOnly: return new SyncAjaxSessionReadOnlyHandler(page, cacheMethodInfo); case SessionState.ReadWrite: return new SyncAjaxSessionHandler(page, cacheMethodInfo); default: return new SyncAjaxHandler(page, cacheMethodInfo); } } } //支持只读Session internal class SyncAjaxSessionReadOnlyHandler : SyncAjaxHandler, IReadOnlySessionState { internal SyncAjaxSessionReadOnlyHandler(Page page, CacheMethodInfo cacheMethodInfo) : base(page, cacheMethodInfo) { } } //支持读写Session internal class SyncAjaxSessionHandler : SyncAjaxHandler, IRequiresSessionState { internal SyncAjaxSessionHandler(Page page, CacheMethodInfo cacheMethodInfo) : base(page, cacheMethodInfo) { } }
异步状态的Handler：
//不支持Session internal class ASyncAjaxHandler : IHttpAsyncHandler, IHttpHandler { private Page _page; private CacheMethodInfo _cacheMethodInfo; internal ASyncAjaxHandler(Page page, CacheMethodInfo cacheMethodInfo) { _page = page; _cacheMethodInfo = cacheMethodInfo; } public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData) { //执行方法(下面详细介绍) Action<Page, HttpContext, CacheMethodInfo> action = new Action<Page, HttpContext, CacheMethodInfo>(Executor.Execute); IAsyncResult result = action.BeginInvoke(_page, context, _cacheMethodInfo, cb, action); return result; } public void EndProcessRequest(IAsyncResult result) { Action<Page, HttpContext, CacheMethodInfo> action = result.AsyncState as Action<Page, HttpContext, CacheMethodInfo>; action.EndInvoke(result); } public void ProcessRequest(HttpContext context) { throw new NotImplementedException(); } public bool IsReusable { get { return false; } } public static ASyncAjaxHandler CreateHandler(Page page, CacheMethodInfo cacheMethodInfo, SessionState state) { switch (state) { case SessionState.ReadOnly: return new ASyncAjaxSessionReadOnlyHandler(page, cacheMethodInfo); case SessionState.ReadWrite: return new ASyncAjaxSessionHandler(page, cacheMethodInfo); default: return new ASyncAjaxHandler(page, cacheMethodInfo); } } } //支持只读Session internal class ASyncAjaxSessionReadOnlyHandler : ASyncAjaxHandler, IReadOnlySessionState { internal ASyncAjaxSessionReadOnlyHandler(Page page, CacheMethodInfo cacheMethodInfo) : base(page, cacheMethodInfo) { } } //支持读写Session internal class ASyncAjaxSessionHandler : ASyncAjaxHandler, IRequiresSessionState { internal ASyncAjaxSessionHandler(Page page, CacheMethodInfo cacheMethodInfo) : base(page, cacheMethodInfo) { } }
AjaxHandlerFactory实现了IHandlerFactory接口，用来根据请求生成具体的Handler，它需要在web.config进行注册使用。AjaxHandlerFactory的GetHandler是我们拦截请求的第一步。通过请求头的AjaxFlag:XHR来判断是否需要我们处理，如果是，则创建一个Handler，否则按照普通的方式进行。由于我们的方法是写在.aspx.cs内的，我们的请求是.aspx后缀的，也就是页面(Page，实现了IHttpHandler)类型，Page是通过PageHandlerFactory创建的，PageHandlerFactory也实现了IHandlerFactory接口，表示它是用来创建处理程序的。所以我们需要用PageHandlerFactory来创建一个IHttpHandler，不过PageHandlerFactory的构造函数是protected internal类型的，我们无法直接new一个，所以需要通过一个CommonPageHandlerFactory继承它来实现。
通过PageHandlerFactory获得Page后，结合方法名称，我们就可以反射获取AjaxMethodAttribute标记属性了。然后根据它的相关属性生成具体的Handler。具体代码如下：
internal class CommonPageHandlerFactory : PageHandlerFactory { } internal class AjaxHandlerFactory : IHttpHandlerFactory { public void ReleaseHandler(IHttpHandler handler) { } public IHttpHandler GetHandler(HttpContext context, string requestType, string url, string pathTranslated) { HttpRequest request = context.Request; if (string.Compare(request.Headers[AjaxConfig.Key], AjaxConfig.Value, true) == 0) { //检查函数标记 string methodName = request.Headers[AjaxConfig.MethodName]; if (methodName.IsNullOrEmpty()) { Executor.EndCurrentRequest(context, "方法名称未正确指定！"); return null; } try { CommonPageHandlerFactory ajaxPageHandler = new CommonPageHandlerFactory(); IHttpHandler handler = ajaxPageHandler.GetHandler(context, requestType, url, pathTranslated); Page page = handler as Page; if (page == null) { Executor.EndCurrentRequest(context, "处理程序类型必须是aspx页面！"); return null; } return GetHandler(page, methodName, context); } catch { Executor.EndCurrentRequest(context, url + " 不存在！"); return null; } } if (url.EndsWith(".aspx", StringComparison.CurrentCultureIgnoreCase)) { CommonPageHandlerFactory orgPageHandler = new CommonPageHandlerFactory(); return orgPageHandler.GetHandler(context, requestType, url, pathTranslated); } return null; } /// <summary> /// 获取自定义处理程序 /// </summary> /// <param>处理页面</param> /// <param>处理方法</param> /// <param>当前请求</param> private IHttpHandler GetHandler(Page page, string methodName, HttpContext context) { //根据Page和MethodName进行反射，获取标记属性（下面详细介绍） CacheMethodInfo methodInfo = Executor.GetDelegateInfo(page, methodName); if (methodInfo == null) { Executor.EndCurrentRequest(context, "找不到指定的Ajax方法！"); return null; } AjaxMethodAttribute attribute = methodInfo.AjaxMethodAttribute; if (attribute.ServerCache > 0) { //先查找缓存 object data = CacheHelper.TryGetCache(context); if (data != null) { Executor.EndCurrentRequest(context, data); return null; } } if (attribute.IsAsync) { //异步处理程序 return ASyncAjaxHandler.CreateHandler(page, methodInfo, attribute.SessionState); } return SyncAjaxHandler.CreateHandler(page, methodInfo, attribute.SessionState); } }