在上一篇文章中介绍了dasBlog模板引擎的两个概念Theme和Macro。这一篇文章介绍dasBlog模板引擎的运行过程。
先简单概括一下dasBlog模板引擎的原理。它提供了一个ShareBasePage的页基类，所有的页面类都从这个类派生，在这个类里，进行页面状态的传递和最终页面的生成。可以说，这是整个模板引擎的一个全局控制者。生成的方法是：在ShareBasePage里读取相应的template文件，顺序提取其中的HTML代码和宏进行相应的处理后添加到页面的PlaceHolder中。HTML代码是被添加到Literal后添加，取得宏表达式后，会转换成相应的Control后再添加到PlaceHolder。这就是页面生成的整个过程。
我们先来看看SharedBasePage的构造函数。从里面两个函数名就可以看出，进行的是状态加载和页面初始化的任务。
public SharedBasePage()
{
Init += new EventHandler(this.SessionLoad); Init += new EventHandler(this.SetupPage); 
} SharedBasePager中的Property添加了自定义的PersistentPageStateAttribute属性之后，每次页面加载完成，该属性都会被保存在Cookie中，第一次开始加载的时候又会被读出来。这个读取来的工作就在SessionLoad里完成了，而保存的工作就在SessionStore里完成了。
而SetupPage做的是些全球和参数处理方面的操作。在SetupPage中还完成了一个很重要的工作，加载了Macros类，这个类里包含了一些全局宏。所谓全局宏是指：网站名称，Trackback排行榜等在任何一个页面都会被显示的内容。相对的，有继承自Macros类的DayMacros(显示某日文章列表的页面的宏的集合)，ItemMacros(显示单篇文章的页面宏的集合)，EditMacros(文章编辑页面的宏的集合)。
当SharedBasePage初始化完成之后，就开始正式进入页面生成步骤了。在SharedBasePage里ProcessTemplate方法是做这个工作的。以下是它的源码：
public virtual void ProcessTemplate() { TemplateProcessor templateProcessor = new TemplateProcessor(); string path = Request.PhysicalApplicationPath; //取得当前使用Template对应的文件内容
string templateString = GetPageTemplate(path);
Match match = findBodyTag.Match(templateString);
if ( match.Success )
{
// this section splits the template into a header, body and footer section
// (all above and including <body>, everything between <body></body> and all below and including </body>
//找到<body>的位置
int indexBody = templateString.IndexOf("</body>");
if ( indexBody == -1 )
{
indexBody = templateString.IndexOf("</BODY>");
}
//取得<head>部分
// the header template contains everything above and including the body tag
string headerTemplate=templateString.Substring(0,match.Index+match.Length);
// insert necessary headtags and fix stylesheet relative links
// fix any relative css link tags
//转换地址
headerTemplate = hrefRegEx.Replace(headerTemplate, String.Format("href=\"{0}themes", Utils.GetBaseUrl()));
string baseTag = String.Format("<base href=\"{0}\"></base>\r\n", Utils.GetBaseUrl());
string linkTag = String.Format("<link rel=\"alternate\" type=\"application/rss+xml\" title=\"{2}\" href=\"{0}\" />\r\n<link rel=\"alternate\" type=\"application/atom+xml\" title=\"{2}\" href=\"{1}\" />\r\n", Utils.GetRssUrl(),Utils.GetAtomUrl(),HttpUtility.HtmlEncode(siteConfig.Title));
int indexHead = headerTemplate.IndexOf("</head>");
if ( indexHead == -1 )
{
indexHead = headerTemplate.IndexOf("</HEAD>");
}
// 给<head>部分添加css等
string templateString = GetPageTemplate(path); Match match = findBodyTag.Match(templateString); if ( match.Success ) {
// this section splits the template into a header, body and footer section // (all above and including <body>, everything between <body></body> and all below and including </body> //找到<body>的位置 int indexBody = templateString.IndexOf("</body>"); if ( indexBody == -1 ) { indexBody = templateString.IndexOf("</BODY>"); } //取得<head>部分 // the header template contains everything above and including the body tag string headerTemplate=templateString.Substring(0,match.Index+match.Length); // insert necessary headtags and fix stylesheet relative links // fix any relative css link tags //转换地址 headerTemplate = hrefRegEx.Replace(headerTemplate, String.Format("href=\"{0}themes", Utils.GetBaseUrl())); string baseTag = String.Format("<base href=\"{0}\"></base>\r\n", Utils.GetBaseUrl()); string linkTag = String.Format("<link rel=\"alternate\" type=\"application/rss+xml\" title=\"{2}\" href=\"{0}\" />\r\n<link rel=\"alternate\" type=\"application/atom+xml\" title=\"{2}\" href=\"{1}\" />\r\n", Utils.GetRssUrl(),Utils.GetAtomUrl(),HttpUtility.HtmlEncode(siteConfig.Title)); int indexHead = headerTemplate.IndexOf("</head>"); if ( indexHead == -1 ) { indexHead = headerTemplate.IndexOf("</HEAD>"); } // 给<head>部分添加css等 headerTemplate = headerTemplate.Insert(indexHead, baseTag.ToString() + linkTag.ToString()); // therefore it must close with a closing angle bracket, but it's better to check if ( headerTemplate[headerTemplate.Length-1] == '>' ) { // if that's so, we want to inject the reading order designator if we're right-to-left // or it's explicitly specified string pageReadingDirection = coreStringTables.GetString("page_reading_direction"); if ( pageReadingDirection != null && pageReadingDirection.Length > 0 ) { if (pageReadingDirection == "RTL") this.readingDirection = TextDirection.RightToLeft; headerTemplate = headerTemplate.Substring(0, headerTemplate.Length-1) + " dir=\"" + pageReadingDirection + "\">"; } } string bodyTemplate,footerTemplate; if( indexBody != -1 ) { //取得template中的主体部分
bodyTemplate=templateString.Substring(match.Index+match.Length,indexBody-(match.Index+match.Length));
bodyTemplate=templateString.Substring(match.Index+match.Length,indexBody-(match.Index+match.Length)); // 取得template中的footer部分
footerTemplate=templateString.Substring(indexBody);
}
else
{
bodyTemplate=templateString.Substring(match.Index+match.Length);
footerTemplate="";
}
// 对headerTemplate进行宏处理，添加到页面的PlaceHolder中
templateProcessor.ProcessTemplate( this, headerTemplate, ContentPlaceHolder, macros );
footerTemplate=templateString.Substring(indexBody); } else { bodyTemplate=templateString.Substring(match.Index+match.Length); footerTemplate=""; } // 对headerTemplate进行宏处理，添加到页面的PlaceHolder中 templateProcessor.ProcessTemplate( this, headerTemplate, ContentPlaceHolder, macros ); // 初始化一个Form
BaseHtmlForm mainForm = new BaseHtmlForm();
mainForm.ID = "mainForm";
BaseHtmlForm mainForm = new BaseHtmlForm(); mainForm.ID = "mainForm"; // 将mainForm添加到PlaceHolder中
ContentPlaceHolder.Controls.Add(mainForm);
// 对bodyTemplate进行宏处理，添加到mainForm中
templateProcessor.ProcessTemplate( this, bodyTemplate, mainForm, macros );
// 对footerTemplate进行宏处理，添加到页面的PlaceHolder中
if ( footerTemplate.Length > 0 )
{
templateProcessor.ProcessTemplate( this, footerTemplate, ContentPlaceHolder, macros );
}
}
else
{
// if the page is just an unrecognizable mess of tags, process in one shot.
templateProcessor.ProcessTemplate( this, templateString, ContentPlaceHolder, macros );
}
}
ContentPlaceHolder.Controls.Add(mainForm); // 对bodyTemplate进行宏处理，添加到mainForm中 templateProcessor.ProcessTemplate( this, bodyTemplate, mainForm, macros ); // 对footerTemplate进行宏处理，添加到页面的PlaceHolder中 if ( footerTemplate.Length > 0 ) { templateProcessor.ProcessTemplate( this, footerTemplate, ContentPlaceHolder, macros ); } } else { // if the page is just an unrecognizable mess of tags, process in one shot. templateProcessor.ProcessTemplate( this, templateString, ContentPlaceHolder, macros ); } }在这个方法里，只是进行了整个生成流程的控制，第一步工作当然是取得模板文件了。
string templateString = GetPageTemplate(path);模板文件的获取是在Theme类里面完成了的。Theme里的OpenTemplate()函数返回一个TextReader对象，在SharedBasePage里读成string，页面生成的过程就是对这个string进行操作了。而真正生成页面的工作是在TemplateProcessor这个类里完成的。而TemplateProcessor里起主要作用的其实也只是一个ProcessTemplate方法，其代码如下：
public void ProcessTemplate(SharedBasePage page, Entry entry, string templateString, Control contentPlaceHolder, Macros macros) { int lastIndex = 0; MatchCollection matches = templateFinder.Matches(templateString); foreach( Match match in matches ) { //添加宏之外的其它字符串 if ( match.Index > lastIndex ) { contentPlaceHolder.Controls.Add(new LiteralControl(templateString.Substring(lastIndex,match.Index-lastIndex))); } Group g = match.Groups["macro"]; Capture c = g.Captures[0]; Control ctrl = null; object targetMacroObj = macros; string captureValue = c.Value; //Check for a string like: <%foo("bar", "bar")|assemblyConfigName%> int assemblyNameIndex = captureValue.IndexOf(")|"); //是否是自定义宏 if (assemblyNameIndex != -1) //use the default Macros { //The QN minus the )| //取得自定义assemblyName string macroAssemblyName = captureValue.Substring(assemblyNameIndex+2); //The method, including the ) //取得宏名称 captureValue = captureValue.Substring(0,assemblyNameIndex+1); //生成自定义宏对象 try { targetMacroObj = MacrosFactory.CreateCustomMacrosInstance(page, entry, macroAssemblyName); } catch (Exception ex) { page.LoggingService.AddEvent(new EventDataItem(EventCodes.Error,String.Format("Error executing Macro: {0}",ex.ToString()),string.Empty)); } } try { //执行宏，返回一个对象 ctrl = InvokeMacro(targetMacroObj,captureValue) as Control; if (ctrl != null) { contentPlaceHolder.Controls.Add(ctrl); } else { page.LoggingService.AddEvent(new EventDataItem(EventCodes.Error,String.Format("Error executing Macro: {0} returned null.",captureValue),string.Empty)); } } catch (Exception ex) { string error = String.Format("Error executing macro: {0}. Make sure it you're calling it in your BlogTemplate with paratheses like 'myMacro()'. Macros with parameter lists and overloads must be called in this way. Exception: {1}",c.Value, ex.ToString()); page.LoggingService.AddEvent(new EventDataItem(EventCodes.Error,error,string.Empty)); } lastIndex = match.Index+match.Length; } if ( lastIndex < templateString.Length) { //将宏添加到PlacheHolder中 contentPlaceHolder.Controls.Add(new LiteralControl(templateString.Substring(lastIndex,templateString.Length-lastIndex))); } }这里的做的工作就是匹配所有类似<%SiteName%>这样的字符串，把它转化成相应的Control，我把它叫做“执行宏”，执行宏的工作在这里进行：
ctrl = InvokeMacro(targetMacroObj,captureValue) as Control;以下是InvodeMacro代码：
private object InvokeMacro( object obj, string expression ) { //子字符串的开始位置 int subexStartIndex = 0; //子字符串的结束位置 int subexEndIndex = 0; object subexObject = obj; try { do { subexEndIndex = expression.IndexOfAny(new char[]{'.','(','['}, subexStartIndex); if ( subexEndIndex == -1 ) subexEndIndex=expression.Length; //取得当次循环处理的宏的字符串表达式 string subex = expression.Substring(subexStartIndex,subexEndIndex-subexStartIndex); //为下次循环做准备 subexStartIndex = subexEndIndex+1; MemberInfo memberToInvoke; //搜索与子字符串匹配的对象或方法 MemberInfo[] members = subexObject.GetType().FindMembers( MemberTypes.Field|MemberTypes.Method|MemberTypes.Property, BindingFlags.IgnoreCase|BindingFlags.Instance|BindingFlags.Public, new MemberFilter(this.IsMemberEligibleForMacroCall), subex.Trim() ); string[] arglist=null; if ( members.Length == 0 ) { throw new MissingMemberException(subexObject.GetType().FullName,subex.Trim()); } //当当前宏带有参数时,取得当前宏的参数 if ( subexEndIndex<expression.Length && (expression[subexEndIndex] == '[' || expression[subexEndIndex] == '(') ) { arglist = SplitArgs(expression,subexEndIndex, ref subexStartIndex); } //SDH: We REALLY need to refactor this whole Clemens thing - it's getting hairy. memberToInvoke = null; if ( members.Length > 1 ) { foreach(MemberInfo potentialMember in members) { MethodInfo potentialMethod = potentialMember as MethodInfo; if(potentialMethod != null) { ParameterInfo[] parameters = potentialMethod.GetParameters(); if(parameters != null && parameters.Length > 0) { //当参数数量相同时判定为要执行的宏 if(parameters.Length == arglist.Length) { memberToInvoke = potentialMember; break; } } } } } //如果不存在该方法,则使用第一个 if(memberToInvoke == null)//Previous behavior, use the first one. { memberToInvoke = members[0]; } //当要执行的宏是一个属性,类似这样的东西Lupin.或者LUPIN[a,b] if ( memberToInvoke.MemberType == MemberTypes.Property && (subexEndIndex==expression.Length || expression[subexEndIndex] == '.' || expression[subexEndIndex] == '[' )) { PropertyInfo propInfo = memberToInvoke as PropertyInfo; if ( subexEndIndex<expression.Length && expression[subexEndIndex] == '[' ) { System.Reflection.ParameterInfo[] paramInfo = propInfo.GetIndexParameters(); if ( arglist.Length > paramInfo.Length ) { throw new InvalidOperationException(String.Format("Parameter list length mismatch {0}",memberToInvoke.Name)); } object[] oarglist = new object[paramInfo.Length]; for( int n=0;n<arglist.Length;n++) { oarglist[n] = Convert.ChangeType(arglist[n],paramInfo[n].ParameterType); } subexObject = propInfo.GetValue(subexObject,oarglist); } else { subexObject = propInfo.GetValue(subexObject,null); } } else if ( memberToInvoke.MemberType == MemberTypes.Field && (subexEndIndex==expression.Length || expression[subexEndIndex] == '.')) { FieldInfo fieldInfo = memberToInvoke as FieldInfo; subexObject = fieldInfo.GetValue(subexObject); } else if ( memberToInvoke.MemberType == MemberTypes.Method && subexEndIndex<expression.Length && expression[subexEndIndex] == '(' ) { MethodInfo methInfo = memberToInvoke as MethodInfo; System.Reflection.ParameterInfo[] paramInfo = methInfo.GetParameters(); if ( arglist.Length > paramInfo.Length && !(paramInfo.Length>0 && paramInfo[paramInfo.Length-1].ParameterType == typeof(string[]))) { throw new InvalidOperationException(String.Format("Parameter list length mismatch {0}",memberToInvoke.Name)); } object[] oarglist = new object[paramInfo.Length]; for( int n=0;n<arglist.Length;n++) { if ( n == paramInfo.Length-1 && arglist.Length>paramInfo.Length) { string[] paramsArg = new string[arglist.Length-paramInfo.Length+1]; for( int m=n;m<arglist.Length;m++) { paramsArg[m-n] = Convert.ChangeType(arglist[n],typeof(string)) as string; } oarglist[n] = paramsArg; break; } else { oarglist[n] = Convert.ChangeType(arglist[n],paramInfo[n].ParameterType); } } subexObject = methInfo.Invoke(subexObject,oarglist); } } while(subexEndIndex<expression.Length && subexStartIndex < expression.Length); return subexObject==null?new LiteralControl(""):subexObject; } catch( Exception exc ) { ErrorTrace.Trace(System.Diagnostics.TraceLevel.Error,exc); throw; } //return new LiteralControl(""); }这个函数相当于是个超简单的脚本解释引擎，具体的工作流程已经超出来本篇的讨论内容，而且再说下去这篇文章就太长了。。所以，就此打住。dasBlog的模板引擎的实现也解释得差不多了。
