MVC源码分析 - View

2018-06-22 06:09:14来源：未知阅读 ()

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));
    }
}