// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Globalization;
using System.Linq;
using System.Web.Hosting;
using System.Web.Mvc.Properties;
using System.Web.WebPages;
namespace System.Web.Mvc
{
public abstract class VirtualPathProviderViewEngine : IViewEngine
{
// format is ":ViewCacheEntry:{cacheType}:{prefix}:{name}:{controllerName}:{areaName}:"
private const string CacheKeyFormat = ":ViewCacheEntry:{0}:{1}:{2}:{3}:{4}:";
private const string CacheKeyPrefixMaster = "Master";
private const string CacheKeyPrefixPartial = "Partial";
private const string CacheKeyPrefixView = "View";
private static readonly string[] _emptyLocations = new string[0];
private DisplayModeProvider _displayModeProvider;
private Func<VirtualPathProvider> _vppFunc = () => HostingEnvironment.VirtualPathProvider;
internal Func<string, string> GetExtensionThunk = VirtualPathUtility.GetExtension;
private IViewLocationCache _viewLocationCache;
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] AreaMasterLocationFormats { get; set; }
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] AreaPartialViewLocationFormats { get; set; }
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] AreaViewLocationFormats { get; set; }
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] FileExtensions { get; set; }
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] MasterLocationFormats { get; set; }
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] PartialViewLocationFormats { get; set; }
// Neither DefaultViewLocationCache.Null nor a DefaultViewLocationCache instance maintain internal state. Fine
// if multiple threads race to initialize _viewLocationCache.
public IViewLocationCache ViewLocationCache
{
get
{
if (_viewLocationCache == null)
{
if (HttpContext.Current == null || HttpContext.Current.IsDebuggingEnabled)
{
_viewLocationCache = DefaultViewLocationCache.Null;
}
else
{
_viewLocationCache = new DefaultViewLocationCache();
}
}
return _viewLocationCache;
}
set
{
if (value == null)
{
throw Error.ArgumentNull("value");
}
_viewLocationCache = value;
}
}
[SuppressMessage("Microsoft.Performance", "CA1819:PropertiesShouldNotReturnArrays", Justification = "This is a shipped API")]
public string[] ViewLocationFormats { get; set; }
// Likely exists for testing only
protected VirtualPathProvider VirtualPathProvider
{
get { return _vppFunc(); }
set
{
if (value == null)
{
throw Error.ArgumentNull("value");
}
_vppFunc = () => value;
}
}
// Provided for testing only; setter used in BuildManagerViewEngine but only for test scenarios
internal Func<VirtualPathProvider> VirtualPathProviderFunc
{
get { return _vppFunc; }
set
{
if (value == null)
{
throw Error.ArgumentNull("value");
}
_vppFunc = value;
}
}
protected internal DisplayModeProvider DisplayModeProvider
{
get { return _displayModeProvider ?? DisplayModeProvider.Instance; }
set { _displayModeProvider = value; }
}
internal virtual string CreateCacheKey(string prefix, string name, string controllerName, string areaName)
{
return String.Format(CultureInfo.InvariantCulture, CacheKeyFormat,
GetType().AssemblyQualifiedName, prefix, name, controllerName, areaName);
}
internal static string AppendDisplayModeToCacheKey(string cacheKey, string displayMode)
{
// key format is ":ViewCacheEntry:{cacheType}:{prefix}:{name}:{controllerName}:{areaName}:"
// so append "{displayMode}:" to the key
return cacheKey + displayMode + ":";
}
protected abstract IView CreatePartialView(ControllerContext controllerContext, string partialPath);
protected abstract IView CreateView(ControllerContext controllerContext, string viewPath, string masterPath);
protected virtual bool FileExists(ControllerContext controllerContext, string virtualPath)
{
return VirtualPathProvider.FileExists(virtualPath);
}
public virtual ViewEngineResult FindPartialView(ControllerContext controllerContext, string partialViewName, bool useCache)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
if (String.IsNullOrEmpty(partialViewName))
{
throw new ArgumentException(MvcResources.Common_NullOrEmpty, "partialViewName");
}
string[] searched;
string controllerName = controllerContext.RouteData.GetRequiredString("controller");
string partialPath = GetPath(controllerContext, PartialViewLocationFormats, AreaPartialViewLocationFormats, "PartialViewLocationFormats", partialViewName, controllerName, CacheKeyPrefixPartial, useCache, out searched);
if (String.IsNullOrEmpty(partialPath))
{
return new ViewEngineResult(searched);
}
return new ViewEngineResult(CreatePartialView(controllerContext, partialPath), this);
}
//開始開始開始開始開始開始開始開始開始開始開始開始開始開始開始開始開始開始開始開始
//useCache先是true，該方法返回的是null。則讓useCache=false，再執(zhí)行一遍。即：先通過緩存去找，如果沒有找到的話，就正經(jīng)的去找。
public virtual ViewEngineResult FindView(ControllerContext controllerContext, string viewName, string masterName, bool useCache)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
if (String.IsNullOrEmpty(viewName))
{
throw new ArgumentException(MvcResources.Common_NullOrEmpty, "viewName");
}
string[] viewLocationsSearched;
string[] masterLocationsSearched;
string controllerName = controllerContext.RouteData.GetRequiredString("controller");
//獲取視圖的路徑
//ViewLocationFormats、AreaViewLocationFormats定義在派生類RazorViewEngine類中。
//ViewLocationFormats："~/Views/{1}/{0}.cshtml","~/Views/{1}/{0}.vbhtml", "~/Views/Shared/{0}.cshtml","~/Views/Shared/{0}.vbhtml"
//AreaViewLocationFormats："~/Areas/{2}/Views/{1}/{0}.cshtml", "~/Areas/{2}/Views/{1}/{0}.vbhtml", "~/Areas/{2}/Views/Shared/{0}.cshtml","~/Areas/{2}/Views/Shared/{0}.vbhtml"
string viewPath = GetPath(controllerContext, ViewLocationFormats, AreaViewLocationFormats, "ViewLocationFormats", viewName, controllerName, CacheKeyPrefixView, useCache, out viewLocationsSearched);
string masterPath = GetPath(controllerContext, MasterLocationFormats, AreaMasterLocationFormats, "MasterLocationFormats", masterName, controllerName, CacheKeyPrefixMaster, useCache, out masterLocationsSearched);
if (String.IsNullOrEmpty(viewPath) || (String.IsNullOrEmpty(masterPath) && !String.IsNullOrEmpty(masterName)))
{
return new ViewEngineResult(viewLocationsSearched.Union(masterLocationsSearched));
}
return new ViewEngineResult(CreateView(controllerContext, viewPath, masterPath), this);
}
//獲取視圖路徑方法
private string GetPath(ControllerContext controllerContext, string[] locations, string[] areaLocations, string locationsPropertyName, string name, string controllerName, string cacheKeyPrefix, bool useCache, out string[] searchedLocations)
{
searchedLocations = _emptyLocations;
if (String.IsNullOrEmpty(name))
{
return String.Empty;
}
//從RouteData的DataTokens中獲取key為'area’的值
string areaName = AreaHelpers.GetAreaName(controllerContext.RouteData);
bool usingAreas = !String.IsNullOrEmpty(areaName);
//
List<ViewLocation> viewLocations = GetViewLocations(locations, (usingAreas) ? areaLocations : null);
if (viewLocations.Count == 0)
{
throw new InvalidOperationException(String.Format(CultureInfo.CurrentCulture,
MvcResources.Common_PropertyCannotBeNullOrEmpty, locationsPropertyName));
}
bool nameRepresentsPath = IsSpecificPath(name);
string cacheKey = CreateCacheKey(cacheKeyPrefix, name, (nameRepresentsPath) ? String.Empty : controllerName, areaName);
//是否使用緩存，其實就將一個已知的路徑保存在緩存表中，如果是第一次請求，緩存表中什么也么有啊，所以暫且不看它。
if (useCache)
{
//根據(jù)請求上下文獲取可用的DisplayModelProvider
IEnumerable<IDisplayMode> possibleDisplayModes = DisplayModeProvider.GetAvailableDisplayModesForContext(controllerContext.HttpContext, controllerContext.DisplayMode);
foreach (IDisplayMode displayMode in possibleDisplayModes)
{
//displayMode.DisplayModeId就是“Mobile”，即：執(zhí)行DefaultDisplayMode有參數(shù)的構造函數(shù)
string cachedLocation = ViewLocationCache.GetViewLocation(controllerContext.HttpContext, AppendDisplayModeToCacheKey(cacheKey, displayMode.DisplayModeId));
if (cachedLocation == null)
{
// If any matching display mode location is not in the cache, fall back to the uncached behavior, which will repopulate all of our caches.
return null;
}
// A non-empty cachedLocation indicates that we have a matching file on disk. Return that result.
if (cachedLocation.Length > 0)
{
if (controllerContext.DisplayMode == null)
{
controllerContext.DisplayMode = displayMode;
}
return cachedLocation;
}
// An empty cachedLocation value indicates that we don't have a matching file on disk. Keep going down the list of possible display modes.
}
// GetPath is called again without using the cache.
return null;
}
else
{
//如果ViewResult的參數(shù)的第一個字符是：~ 或 /，則執(zhí)行第一個方法，否則執(zhí)行第二個方法！
//第一個方法：直接指定了路徑去尋找
//第二個方法：只通過試圖名稱再拼接路徑去尋找（用到了DisplayModeProvider）
//第二個方法的viewLocations參數(shù)是含有8條數(shù)據(jù)的集合。
return nameRepresentsPath
GetPathFromSpecificName(controllerContext, name, cacheKey, ref searchedLocations)
: GetPathFromGeneralName(controllerContext, viewLocations, name, controllerName, areaName, cacheKey, ref searchedLocations);
}
}
private string GetPathFromGeneralName(ControllerContext controllerContext, List<ViewLocation> locations, string name, string controllerName, string areaName, string cacheKey, ref string[] searchedLocations)
{
string result = String.Empty;
searchedLocations = new string[locations.Count];
for (int i = 0; i < locations.Count; i++)
{
ViewLocation location = locations[i];
//根據(jù)8種格式器創(chuàng)建路徑
string virtualPath = location.Format(name, controllerName, areaName);
//這里的controllerContext.DisplayMode屬性執(zhí)行DisplayModeProvider的GetDisplayMode、SetDisplayMode方法！
DisplayInfo virtualPathDisplayInfo = DisplayModeProvider.GetDisplayInfoForVirtualPath(virtualPath, controllerContext.HttpContext, path => FileExists(controllerContext, path), controllerContext.DisplayMode);
if (virtualPathDisplayInfo != null)
{
string resolvedVirtualPath = virtualPathDisplayInfo.FilePath;
searchedLocations = _emptyLocations;
result = resolvedVirtualPath;
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, AppendDisplayModeToCacheKey(cacheKey, virtualPathDisplayInfo.DisplayMode.DisplayModeId), result);
if (controllerContext.DisplayMode == null)
{
controllerContext.DisplayMode = virtualPathDisplayInfo.DisplayMode;
}
// Populate the cache for all other display modes. We want to cache both file system hits and misses so that we can distinguish
// in future requests whether a file's status was evicted from the cache (null value) or if the file doesn't exist (empty string).
//再執(zhí)行循環(huán)執(zhí)行除了適合的那個DefaultDisplayMode之外的所有DefaultDisplayMode對象，將所有存在的路徑封裝到DisplayInfo對象中，并添加到緩存表中，以便之后請求時直接去緩存中獲取。
//例如：當前是手機的請求，則會通過執(zhí)行DisplayModeId='Mobile’的那個DefaultDisplayMode來獲取【視圖頁】的路徑（Index.Mobile.cshtml），
// 但是在執(zhí)行完成之后，還會執(zhí)行DisplayModeId!='Mobile’所有其他的DefaultDisplayMode對象，也就是pc端請求時的路徑（Index.cshtml），將其加入緩存表中，以便下次請求時直接去緩存表中獲取。
IEnumerable<IDisplayMode> allDisplayModes = DisplayModeProvider.Modes;
foreach (IDisplayMode displayMode in allDisplayModes)
{
if (displayMode.DisplayModeId != virtualPathDisplayInfo.DisplayMode.DisplayModeId)
{
DisplayInfo displayInfoToCache = displayMode.GetDisplayInfo(controllerContext.HttpContext, virtualPath, virtualPathExists: path => FileExists(controllerContext, path));
string cacheValue = String.Empty;
if (displayInfoToCache != null && displayInfoToCache.FilePath != null)
{
cacheValue = displayInfoToCache.FilePath;
}
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, AppendDisplayModeToCacheKey(cacheKey, displayMode.DisplayModeId), cacheValue);
}
}
break;
}
searchedLocations[i] = virtualPath;
}
return result;
}
private string GetPathFromSpecificName(ControllerContext controllerContext, string name, string cacheKey, ref string[] searchedLocations)
{
string result = name;
if (!(FilePathIsSupported(name) && FileExists(controllerContext, name)))
{
result = String.Empty;
searchedLocations = new[] { name };
}
ViewLocationCache.InsertViewLocation(controllerContext.HttpContext, cacheKey, result);
return result;
}
private bool FilePathIsSupported(string virtualPath)
{
if (FileExtensions == null)
{
// legacy behavior for custom ViewEngine that might not set the FileExtensions property
return true;
}
else
{
// get rid of the '.' because the FileExtensions property expects extensions withouth a dot.
string extension = GetExtensionThunk(virtualPath).TrimStart('.');
return FileExtensions.Contains(extension, StringComparer.OrdinalIgnoreCase);
}
}
private static List<ViewLocation> GetViewLocations(string[] viewLocationFormats, string[] areaViewLocationFormats)
{
//將四個AreaAwareViewLocation和四個ViewLocation添加到 allLocations集合中！并返回
//AreaAwareViewLocation繼承自ViewLocation
List<ViewLocation> allLocations = new List<ViewLocation>();
if (areaViewLocationFormats != null)
{
foreach (string areaViewLocationFormat in areaViewLocationFormats)
{
allLocations.Add(new AreaAwareViewLocation(areaViewLocationFormat));
}
}
if (viewLocationFormats != null)
{
foreach (string viewLocationFormat in viewLocationFormats)
{
allLocations.Add(new ViewLocation(viewLocationFormat));
}
}
return allLocations;
}
private static bool IsSpecificPath(string name)
{
char c = name[0];
return (c == '~' || c == '/');
}
public virtual void ReleaseView(ControllerContext controllerContext, IView view)
{
IDisposable disposable = view as IDisposable;
if (disposable != null)
{
disposable.Dispose();
}
}
private class AreaAwareViewLocation : ViewLocation
{
public AreaAwareViewLocation(string virtualPathFormatString)
: base(virtualPathFormatString)
{
}
public override string Format(string viewName, string controllerName, string areaName)
{
return String.Format(CultureInfo.InvariantCulture, _virtualPathFormatString, viewName, controllerName, areaName);
}
}
private class ViewLocation
{
protected string _virtualPathFormatString;
public ViewLocation(string virtualPathFormatString)
{
_virtualPathFormatString = virtualPathFormatString;
}
public virtual string Format(string viewName, string controllerName, string areaName)
{
return String.Format(CultureInfo.InvariantCulture, _virtualPathFormatString, viewName, controllerName);
}
}
}
}
