【AjaxPro实现机制浅析二】*.ashx文件是怎么来的？

上篇 说到AjaxPro为我们生成了四个ashx文件来达到异步调用的目的，这次呢，就说说这些ashx文件是怎么生成的；

核心部分是其web.config配置了httpHandlers 元素

<httpHandlers>
      <add verb="POST,GET" path="ajaxpro/*.ashx" type="AjaxPro.AjaxHandlerFactory, AjaxPro"/>
</httpHandlers>

作用是：对ajaxpro目录下的*.ashx文件的POST,GET请求交由程序集AjaxPro下的AjaxPro.AjaxHandlerFactory类来处理；

ps:关于httpHandlers的说明可以参看下面几个连接
1.httpHandlers 元素（ASP.NET 设置架构）
2.Microsoft ASP.NET 快速入门教程
3.ASP.NET中的Http Handles

先看看实现IHttpHandlerFactory接口的AjaxHandlerFactory类，只实现了GetHandler方法

其中对core，prototype的处理没什么可说，只是简单的通过EmbeddedJavaScriptHandler的ProcessRequest中将js写入.ashx文件，而converter比较复杂留代下次再做详细分析；这里就重点看看AJAXDemo.Examples.Test.TestMethod,App_Code.urx4hqkg.ashx是怎么来的了；

我跟踪了下代码的运行，在页面加载的时候自定义 HttpHandler 启用 HTTP Web 请求的处理ProcessRequest，也就是进入AjaxHandlerFactory类GetHandler方法的如下入口

default:

                            if(Utility.Settings.UrlNamespaceMappings.Contains(filename))
                                t = Type.GetType(Utility.Settings.UrlNamespaceMappings[filename].ToString());

                            if(t == null)
                                t = Type.GetType(filename);

                            return new TypeJavaScriptHandler(t);

TypeJavaScriptHandler也实现了IHttpHandler接口，其ProcessRequest方法如下：

public void ProcessRequest(HttpContext context)
        {
            // The request was not a request to invoke a server-side method.
            // Now, we will render the Javascript that will be used on the
            // client to run as a proxy or wrapper for the methods marked
            // with the AjaxMethodAttribute.

            if(context.Trace.IsEnabled) context.Trace.Write(Constant.AjaxID, "Render class proxy Javascript");
        
            System.Reflection.MethodInfo[] mi = type.GetMethods();
            
            // Check wether the javascript is already rendered and cached in the
            // current context.
            
            string etag = context.Request.Headers["If-None-Match"];
            string modSince = context.Request.Headers["If-Modified-Since"];
            string path = type.FullName + "," + type.Assembly.FullName.Split(',')[0];

            if(Utility.Settings != null && Utility.Settings.UrlNamespaceMappings.ContainsValue(path))
            {
                foreach(string key in Utility.Settings.UrlNamespaceMappings.Keys)
                {
                    if(Utility.Settings.UrlNamespaceMappings[key].ToString() == path)
                    {
                        path = key;
                        break;
                    }
                }
            }

            if(context.Cache[path] != null)
            {
                CacheInfo ci = (CacheInfo)context.Cache[path];

                if(etag != null)
                {
                    if(etag == ci.ETag)        // TODO: null check
                    {
                        context.Response.StatusCode = 304;
                        return;
                    }
                }
                
                if(modSince != null)
                {
                    try
                    {
                        DateTime modSinced = Convert.ToDateTime(modSince.ToString()).ToUniversalTime();
                        if(DateTime.Compare(modSinced, ci.LastModified.ToUniversalTime()) >= 0)
                        {
                            context.Response.StatusCode = 304;
                            return;
                        }
                    }
                    catch(Exception)
                    {
                        if(context.Trace.IsEnabled) context.Trace.Write(Constant.AjaxID, "The header value for If-Modified-Since = " + modSince + " could not be converted to a System.DateTime.");
                    }
                }
            }

            etag = type.AssemblyQualifiedName; // + "_" + type.Assembly. DateTime.Now.ToString(System.Globalization.DateTimeFormatInfo.CurrentInfo.SortableDateTimePattern);
            etag = MD5Helper.GetHash(System.Text.Encoding.Default.GetBytes(etag));

            DateTime now = DateTime.Now;
            DateTime lastMod = new DateTime(now.Year, now.Month, now.Day, now.Hour, now.Minute, now.Second); // .ToUniversalTime();

            context.Response.AddHeader("Content-Type", "application/x-javascript");
            context.Response.ContentEncoding = System.Text.Encoding.UTF8;
            context.Response.Cache.SetCacheability(System.Web.HttpCacheability.Public);
            context.Response.Cache.SetETag(etag);
            context.Response.Cache.SetLastModified(lastMod);

            // Ok, we do not have the javascript rendered, yet.
            // Build the javascript source and save it to the current
            // Application context.

            System.Text.StringBuilder sb = new System.Text.StringBuilder();


            AjaxNamespaceAttribute[] cma = (AjaxNamespaceAttribute[])type.GetCustomAttributes(typeof(AjaxNamespaceAttribute), true);
            string clientNS = type.FullName;

            if(cma.Length > 0 && cma[0].ClientNamespace != null)
            {
                if(cma[0].ClientNamespace.IndexOf(".") > 0)
                    sb.Append("addNamespace(\"" + cma[0].ClientNamespace + "\");\r\n");

                clientNS = cma[0].ClientNamespace;
            }
            else
            {
                sb.Append("addNamespace(\"" + (type.FullName.IndexOf(".") > 0 ? type.FullName.Substring(0, type.FullName.LastIndexOf(".")) : type.FullName) + "\");\r\n");
            }

            sb.Append(clientNS);
            sb.Append("_class = Class.create();\r\n");

            sb.Append(clientNS);
            sb.Append("_class.prototype = (new AjaxPro.AjaxClass()).extend({\r\n");

            System.Reflection.MethodInfo method;

            for(int y=0; y<mi.Length; y++)
            {
                method = mi[y];

                if(!method.IsPublic)
                    continue;

                AjaxNamespaceAttribute[] cmam = (AjaxNamespaceAttribute[])method.GetCustomAttributes(typeof(AjaxNamespaceAttribute), true);
                AjaxMethodAttribute[] ma = (AjaxMethodAttribute[])method.GetCustomAttributes(typeof(AjaxMethodAttribute), true);

                if(ma.Length == 0)
                    continue;

                System.Reflection.ParameterInfo[] pi = method.GetParameters();

                // Render the function header

                sb.Append("\t");

                if(cmam.Length == 0)
                    sb.Append(method.Name);
                else
                    sb.Append(cmam[0].ClientNamespace);

                sb.Append(": function(");


                // Render all parameters

                for(int i=0; i<pi.Length; i++)
                {
                    sb.Append(pi[i].Name);

                    if(i<pi.Length -1)
                        sb.Append(", ");
                }
    
                sb.Append(") {\r\n");


                // Create the XMLHttpRequest object

                sb.Append("\t\treturn this.invoke(\"" + method.Name + "\", {");        // must be the original method name

                for(int i=0; i<pi.Length; i++)
                {
                    sb.Append("\"");
                    sb.Append(pi[i].Name);
                    sb.Append("\":");
                    sb.Append(pi[i].Name);

                    if(i<pi.Length -1)
                        sb.Append(", ");
                }

                sb.Append("}, this.");
                
                if(cmam.Length == 0)
                    sb.Append(method.Name);
                else
                    sb.Append(cmam[0].ClientNamespace);

                sb.Append(".getArguments().slice(");
                sb.Append(pi.Length.ToString());
                sb.Append("));\r\n\t},\r\n");
            }

            string url = context.Request.ApplicationPath + (context.Request.ApplicationPath.EndsWith("/") ? "" : "/") + Utility.HandlerPath + "/" + (context.Session != null && context.Session.IsCookieless ? "(" + context.Session.SessionID + ")/" : "") + path + Utility.HandlerExtension;

            sb.Append("\tinitialize: function() {\r\n\t\tthis.url = '" + url + "';\r\n\t}\r\n");
            sb.Append("});\r\n");


            sb.Append(clientNS);
            sb.Append(" = new ");
            sb.Append(clientNS);
            sb.Append("_class();\r\n");


            // save the javascript in current Application context to
            // speed up the next requests.

            // TODO: was knen wir hier machen??
            // System.Web.Caching.CacheDependency fileDepend = new System.Web.Caching.CacheDependency(type.Assembly.Location);

            context.Cache.Add(path, new CacheInfo(etag, lastMod), null, 
                System.Web.Caching.Cache.NoAbsoluteExpiration, System.Web.Caching.Cache.NoSlidingExpiration,
                System.Web.Caching.CacheItemPriority.Normal, null);

            context.Response.Write(sb.ToString());
            context.Response.Write("\r\n");

            
            if(context.Trace.IsEnabled) context.Trace.Write(Constant.AjaxID, "End ProcessRequest");
        }

代码很明了，只是注释少了点，可能是作者认为没什么难理解的吧，感兴趣的可以到http://www.ajaxpro.info/找源代码跟踪一下，具体的运行过程，可能就更明白是怎么回事了，下篇该来说说这些ashx是用来干什么的了！