MVC源码分析 - View
感觉好久没有学习了, 汗. 年就这么过完了, 感觉没有尝到过年的味道. 现在的年过的有些冷清了.
除了体重证明着我过了一个年, 还有一件值得开心的事情, 终于把女朋友变成未婚妻了. 这是一大进步吧.
闲话不扯了, 继续之前没有完成的学习.
前面 结尾处, 提到了这个方法:
protected virtual void InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) { actionResult.ExecuteResult(controllerContext); }
ExecuteResult方法是一个抽象方法. 那么来看一下, 都是有哪些类中来实现了这一方法.
这里的这些类, 应该还是让人蛮熟悉的吧. 在Action方法中, return View() / Json() / Content() / File() ...
这里的这些返回方式, 只有View()是还要去查找视图, 解析视图, 然后返回视图的, 所以先来看这个了.
一、View
//System.Web.Mvc.ViewResultBase
public override void ExecuteResult(ControllerContext context) { if (context == null) { throw new ArgumentNullException("context"); } if (string.IsNullOrEmpty(this.ViewName)) { this.ViewName = context.RouteData.GetRequiredString("action"); } ViewEngineResult result = null; if (this.View == null) { result = this.FindView(context); this.View = result.View; } TextWriter output = context.HttpContext.Response.Output; ViewContext viewContext = new ViewContext(context, this.View, this.ViewData, this.TempData, output); this.View.Render(viewContext, output); if (result != null) { result.ViewEngine.ReleaseView(context, this.View); } }
1. FindView(context)
这个方法也是一个抽象方法. 其实现类为: System.Web.Mvc.PartialViewResult 和 System.Web.Mvc.ViewResult.
这个方法就是去负责查找需要使用到的视图.
看一下ViewResult类中, 最终调用的方法
//System.Web.Mvc.VirtualPathProviderViewEngine public virtual ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache) { string[] strArray; string[] strArray2; if (controllerContext == null) { throw new ArgumentNullException("controllerContext"); } if (string.IsNullOrEmpty(viewName)) { throw new ArgumentException(MvcResources.Common_NullOrEmpty, "viewName"); } string requiredString = controllerContext.RouteData.GetRequiredString("controller"); string str2 = this.GetPath(controllerContext, this.ViewLocationFormats, this.AreaViewLocationFormats, "ViewLocationFormats", viewName, requiredString, "View", useCache, out strArray); string str3 = this.GetPath(controllerContext, this.MasterLocationFormats, this.AreaMasterLocationFormats, "MasterLocationFormats", masterName, requiredString, "Master", useCache, out strArray2); if (!string.IsNullOrEmpty(str2) && (!string.IsNullOrEmpty(str3) || string.IsNullOrEmpty(masterName))) { return new ViewEngineResult(this.CreateView(controllerContext, str2, str3), this); } return new ViewEngineResult(strArray.Union<string>(strArray2)); }
查找到视图之后, 创建一个视图引擎, 然后返回这个视图引擎.
2. Render(viewContext, output)
这个方法就是去解析视图, 主要是为了解析其中的Razor, 生成最后的页面数据.
//System.Web.Mvc.BuildManagerCompiledView public void Render(ViewContext viewContext, TextWriter writer) { if (viewContext == null) { throw new ArgumentNullException("viewContext"); } object instance = null; Type compiledType = this.BuildManager.GetCompiledType(this.ViewPath); if (compiledType != null) { instance = this.ViewPageActivator.Create(this._controllerContext, compiledType); } if (instance == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.CshtmlView_ViewCouldNotBeCreated, new object[] { this.ViewPath })); } this.RenderView(viewContext, writer, instance); }
这里的RenderView也有两种实现类, 我们在vs中建mvc项目的时候, 可能有人注意到过, 视图有两种模式可以选, 一种是Razor, 另一种就是WebForm. 事实上, 确实是有两种语法以供使用的.
那这里只看一下Razor的语法了.
//System.Web.Mvc.RazorView
protected override void RenderView(ViewContext viewContext, TextWriter writer, object instance) { if (writer == null) { throw new ArgumentNullException("writer"); } WebViewPage page = instance as WebViewPage; if (page == null) { throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, MvcResources.CshtmlView_WrongViewBase, new object[] { base.ViewPath })); } page.OverridenLayoutPath = this.LayoutPath; page.VirtualPath = base.ViewPath; page.ViewContext = viewContext; page.ViewData = viewContext.ViewData; page.InitHelpers(); if (this.VirtualPathFactory != null) { page.VirtualPathFactory = this.VirtualPathFactory; } if (this.DisplayModeProvider != null) { page.DisplayModeProvider = this.DisplayModeProvider; } WebPageRenderingBase startPage = null; if (this.RunViewStartPages) { startPage = this.StartPageLookup(page, RazorViewEngine.ViewStartFileName, this.ViewStartFileExtensions); } HttpContextBase httpContext = viewContext.HttpContext; WebPageRenderingBase base4 = null; object model = null; page.ExecutePageHierarchy(new WebPageContext(httpContext, base4, model), writer, startPage); }
3. ReleaseView(context, this.View)
//System.Web.Mvc.VirtualPathProviderViewEngine public virtual void ReleaseView(ControllerContext controllerContext, IView view) { IDisposable disposable = view as IDisposable; if (disposable != null) { disposable.Dispose(); } }
这里是释放资源了
二、Json
这个也是常用的, 返回时, 会在内部转换实体为Json格式字符串. 非常方便好用. 为前端直接提供数据.
public override void ExecuteResult(ControllerContext context) { if (context == null) { throw new ArgumentNullException("context"); } if ((this.JsonRequestBehavior == JsonRequestBehavior.DenyGet) && string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase)) { throw new InvalidOperationException(MvcResources.JsonRequest_GetNotAllowed); } HttpResponseBase response = context.HttpContext.Response; if (!string.IsNullOrEmpty(this.ContentType)) { response.ContentType = this.ContentType; } else { response.ContentType = "application/json"; } if (this.ContentEncoding != null) { response.ContentEncoding = this.ContentEncoding; } if (this.Data != null) { JavaScriptSerializer serializer = new JavaScriptSerializer(); if (this.MaxJsonLength.HasValue) { serializer.MaxJsonLength = this.MaxJsonLength.Value; } if (this.RecursionLimit.HasValue) { serializer.RecursionLimit = this.RecursionLimit.Value; } response.Write(serializer.Serialize(this.Data)); } }
