// Copyright (c) .NET Foundation. All rights reserved. // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information. using System; using System.Collections.Generic; using System.Diagnostics; using System.Globalization; using System.Linq; using System.Text.Encodings.Web; using Microsoft.AspNetCore.Mvc.Routing; using Microsoft.AspNetCore.Mvc.ViewEngines; using Microsoft.Extensions.Caching.Memory; using Microsoft.Extensions.Logging; using Microsoft.Extensions.Options; using Microsoft.Extensions.Primitives; namespace Microsoft.AspNetCore.Mvc.Razor { /// <summary> /// Default implementation of <see cref="IRazorViewEngine"/>. /// </summary> /// <remarks> /// For <c>ViewResults</c> returned from controllers, views should be located in /// <see cref="RazorViewEngineOptions.ViewLocationFormats"/> /// by default. For the controllers in an area, views should exist in /// <see cref="RazorViewEngineOptions.AreaViewLocationFormats"/>. /// </remarks> public class RazorViewEngine : IRazorViewEngine { public static readonly string ViewExtension = ".cshtml"; private const string AreaKey = "area"; private const string ControllerKey = "controller"; private const string PageKey = "page"; private static readonly TimeSpan _cacheExpirationDuration = TimeSpan.FromMinutes(20); private readonly IRazorPageFactoryProvider _pageFactory; private readonly IRazorPageActivator _pageActivator; private readonly HtmlEncoder _htmlEncoder; private readonly ILogger _logger; private readonly RazorViewEngineOptions _options; private readonly DiagnosticListener _diagnosticListener; /// <summary> /// Initializes a new instance of the <see cref="RazorViewEngine" />. /// </summary> public RazorViewEngine( IRazorPageFactoryProvider pageFactory, IRazorPageActivator pageActivator, HtmlEncoder htmlEncoder, IOptions<RazorViewEngineOptions> optionsAccessor, ILoggerFactory loggerFactory, DiagnosticListener diagnosticListener) { _options = optionsAccessor.Value; if (_options.ViewLocationFormats.Count == 0) { throw new ArgumentException( Resources.FormatViewLocationFormatsIsRequired(nameof(RazorViewEngineOptions.ViewLocationFormats)), nameof(optionsAccessor)); } if (_options.AreaViewLocationFormats.Count == 0) { throw new ArgumentException( Resources.FormatViewLocationFormatsIsRequired(nameof(RazorViewEngineOptions.AreaViewLocationFormats)), nameof(optionsAccessor)); } _pageFactory = pageFactory; _pageActivator = pageActivator; _htmlEncoder = htmlEncoder; _logger = loggerFactory.CreateLogger<RazorViewEngine>(); _diagnosticListener = diagnosticListener; ViewLookupCache = new MemoryCache(new MemoryCacheOptions()); } /// <summary> /// A cache for results of view lookups. /// </summary> protected IMemoryCache ViewLookupCache { get; } /// <summary> /// Gets the case-normalized route value for the specified route <paramref/>. /// </summary> /// <param>The <see cref="ActionContext"/>.</param> /// <param>The route key to lookup.</param> /// <returns>The value corresponding to the key.</returns> /// <remarks> /// The casing of a route value in <see cref="ActionContext.RouteData"/> is determined by the client. /// This making constructing paths for view locations in a case sensitive file system unreliable. Using the /// <see cref="Abstractions.ActionDescriptor.RouteValues"/> to get route values /// produces consistently cased results. /// </remarks> public static string GetNormalizedRouteValue(ActionContext context, string key) => NormalizedRouteValue.GetNormalizedRouteValue(context, key); /// <inheritdoc /> public RazorPageResult FindPage(ActionContext context, string pageName) { if (context == null) { throw new ArgumentNullException(nameof(context)); } if (string.IsNullOrEmpty(pageName)) { throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(pageName)); } if (IsApplicationRelativePath(pageName) || IsRelativePath(pageName)) { // A path; not a name this method can handle. return new RazorPageResult(pageName, Enumerable.Empty<string>()); } var cacheResult = LocatePageFromViewLocations(context, pageName, isMainPage: false); if (cacheResult.Success) { var razorPage = cacheResult.ViewEntry.PageFactory(); return new RazorPageResult(pageName, razorPage); } else { return new RazorPageResult(pageName, cacheResult.SearchedLocations); } } /// <inheritdoc /> public RazorPageResult GetPage(string executingFilePath, string pagePath) { if (string.IsNullOrEmpty(pagePath)) { throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(pagePath)); } if (!(IsApplicationRelativePath(pagePath) || IsRelativePath(pagePath))) { // Not a path this method can handle. return new RazorPageResult(pagePath, Enumerable.Empty<string>()); } var cacheResult = LocatePageFromPath(executingFilePath, pagePath, isMainPage: false); if (cacheResult.Success) { var razorPage = cacheResult.ViewEntry.PageFactory(); return new RazorPageResult(pagePath, razorPage); } else { return new RazorPageResult(pagePath, cacheResult.SearchedLocations); } } /// <inheritdoc /> public ViewEngineResult FindView(ActionContext context, string viewName, bool isMainPage) { if (context == null) { throw new ArgumentNullException(nameof(context)); } if (string.IsNullOrEmpty(viewName)) { throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(viewName)); } if (IsApplicationRelativePath(viewName) || IsRelativePath(viewName)) { // A path; not a name this method can handle. return ViewEngineResult.NotFound(viewName, Enumerable.Empty<string>()); } var cacheResult = LocatePageFromViewLocations(context, viewName, isMainPage); return CreateViewEngineResult(cacheResult, viewName); } /// <inheritdoc /> public ViewEngineResult GetView(string executingFilePath, string viewPath, bool isMainPage) { if (string.IsNullOrEmpty(viewPath)) { throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(viewPath)); } if (!(IsApplicationRelativePath(viewPath) || IsRelativePath(viewPath))) { // Not a path this method can handle. return ViewEngineResult.NotFound(viewPath, Enumerable.Empty<string>()); } var cacheResult = LocatePageFromPath(executingFilePath, viewPath, isMainPage); return CreateViewEngineResult(cacheResult, viewPath); } private ViewLocationCacheResult LocatePageFromPath(string executingFilePath, string pagePath, bool isMainPage) { var applicationRelativePath = GetAbsolutePath(executingFilePath, pagePath); var cacheKey = new ViewLocationCacheKey(applicationRelativePath, isMainPage); if (!ViewLookupCache.TryGetValue(cacheKey, out ViewLocationCacheResult cacheResult)) { var expirationTokens = new HashSet<IChangeToken>(); cacheResult = CreateCacheResult(expirationTokens, applicationRelativePath, isMainPage); var cacheEntryOptions = new MemoryCacheEntryOptions(); cacheEntryOptions.SetSlidingExpiration(_cacheExpirationDuration); foreach (var expirationToken in expirationTokens) { cacheEntryOptions.AddExpirationToken(expirationToken); } // No views were found at the specified location. Create a not found result. if (cacheResult == null) { cacheResult = new ViewLocationCacheResult(new[] { applicationRelativePath }); } cacheResult = ViewLookupCache.Set( cacheKey, cacheResult, cacheEntryOptions); } return cacheResult; } private ViewLocationCacheResult LocatePageFromViewLocations( ActionContext actionContext, string pageName, bool isMainPage) { var controllerName = GetNormalizedRouteValue(actionContext, ControllerKey); var areaName = GetNormalizedRouteValue(actionContext, AreaKey); string razorPageName = null; if (actionContext.ActionDescriptor.RouteValues.ContainsKey(PageKey)) { // Only calculate the Razor Page name if "page" is registered in RouteValues. razorPageName = GetNormalizedRouteValue(actionContext, PageKey); } var expanderContext = new ViewLocationExpanderContext( actionContext, pageName, controllerName, areaName, razorPageName, isMainPage); Dictionary<string, string> expanderValues = null; var expanders = _options.ViewLocationExpanders; // Read interface .Count once rather than per iteration var expandersCount = expanders.Count; if (expandersCount > 0) { expanderValues = new Dictionary<string, string>(StringComparer.Ordinal); expanderContext.Values = expanderValues; // Perf: Avoid allocations for (var i = 0; i < expandersCount; i++) { expanders[i].PopulateValues(expanderContext); } } var cacheKey = new ViewLocationCacheKey( expanderContext.ViewName, expanderContext.ControllerName, expanderContext.AreaName, expanderContext.PageName, expanderContext.IsMainPage, expanderValues); if (!ViewLookupCache.TryGetValue(cacheKey, out ViewLocationCacheResult cacheResult)) { _logger.ViewLookupCacheMiss(cacheKey.ViewName, cacheKey.ControllerName); cacheResult = OnCacheMiss(expanderContext, cacheKey); } else { _logger.ViewLookupCacheHit(cacheKey.ViewName, cacheKey.ControllerName); } return cacheResult; } /// <inheritdoc /> public string GetAbsolutePath(string executingFilePath, string pagePath) { if (string.IsNullOrEmpty(pagePath)) { // Path is not valid; no change required. return pagePath; } if (IsApplicationRelativePath(pagePath)) { // An absolute path already; no change required. return pagePath; } if (!IsRelativePath(pagePath)) { // A page name; no change required. return pagePath; } if (string.IsNullOrEmpty(executingFilePath)) { // Given a relative path i.e. not yet application-relative (starting with "~/" or "https://www.jb51.net/"), interpret // path relative to currently-executing view, if any. // Not yet executing a view. Start in app root. var absolutePath = "https://www.jb51.net/" + pagePath; return ViewEnginePath.ResolvePath(absolutePath); } return ViewEnginePath.CombinePath(executingFilePath, pagePath); } // internal for tests internal IEnumerable<string> GetViewLocationFormats(ViewLocationExpanderContext context) { if (!string.IsNullOrEmpty(context.AreaName) && !string.IsNullOrEmpty(context.ControllerName)) { return _options.AreaViewLocationFormats; } else if (!string.IsNullOrEmpty(context.ControllerName)) { return _options.ViewLocationFormats; } else if (!string.IsNullOrEmpty(context.AreaName) && !string.IsNullOrEmpty(context.PageName)) { return _options.AreaPageViewLocationFormats; } else if (!string.IsNullOrEmpty(context.PageName)) { return _options.PageViewLocationFormats; } else { // If we don't match one of these conditions, we'll just treat it like regular controller/action // and use those search paths. This is what we did in 1.0.0 without giving much thought to it. return _options.ViewLocationFormats; } } private ViewLocationCacheResult OnCacheMiss( ViewLocationExpanderContext expanderContext, ViewLocationCacheKey cacheKey) { var viewLocations = GetViewLocationFormats(expanderContext); var expanders = _options.ViewLocationExpanders; // Read interface .Count once rather than per iteration var expandersCount = expanders.Count; for (var i = 0; i < expandersCount; i++) { viewLocations = expanders[i].ExpandViewLocations(expanderContext, viewLocations); } ViewLocationCacheResult cacheResult = null; var searchedLocations = new List<string>(); var expirationTokens = new HashSet<IChangeToken>(); foreach (var location in viewLocations) { var path = string.Format( CultureInfo.InvariantCulture, location, expanderContext.ViewName, expanderContext.ControllerName, expanderContext.AreaName); path = ViewEnginePath.ResolvePath(path); cacheResult = CreateCacheResult(expirationTokens, path, expanderContext.IsMainPage); if (cacheResult != null) { break; } searchedLocations.Add(path); } // No views were found at the specified location. Create a not found result. if (cacheResult == null) { cacheResult = new ViewLocationCacheResult(searchedLocations); } var cacheEntryOptions = new MemoryCacheEntryOptions(); cacheEntryOptions.SetSlidingExpiration(_cacheExpirationDuration); foreach (var expirationToken in expirationTokens) { cacheEntryOptions.AddExpirationToken(expirationToken); } return ViewLookupCache.Set(cacheKey, cacheResult, cacheEntryOptions); } // Internal for unit testing internal ViewLocationCacheResult CreateCacheResult( HashSet<IChangeToken> expirationTokens, string relativePath, bool isMainPage) { var factoryResult = _pageFactory.CreateFactory(relativePath); var viewDescriptor = factoryResult.ViewDescriptor; if (viewDescriptor?.ExpirationTokens != null) { var viewExpirationTokens = viewDescriptor.ExpirationTokens; // Read interface .Count once rather than per iteration var viewExpirationTokensCount = viewExpirationTokens.Count; for (var i = 0; i < viewExpirationTokensCount; i++) { expirationTokens.Add(viewExpirationTokens[i]); } } if (factoryResult.Success) { // Only need to lookup _ViewStarts for the main page. var viewStartPages = isMainPage ? GetViewStartPages(viewDescriptor.RelativePath, expirationTokens) : Array.Empty<ViewLocationCacheItem>(); return new ViewLocationCacheResult( new ViewLocationCacheItem(factoryResult.RazorPageFactory, relativePath), viewStartPages); } return null; } private IReadOnlyList<ViewLocationCacheItem> GetViewStartPages( string path, HashSet<IChangeToken> expirationTokens) { var viewStartPages = new List<ViewLocationCacheItem>(); foreach (var filePath in RazorFileHierarchy.GetViewStartPaths(path)) { var result = _pageFactory.CreateFactory(filePath); var viewDescriptor = result.ViewDescriptor; if (viewDescriptor?.ExpirationTokens != null) { for (var i = 0; i < viewDescriptor.ExpirationTokens.Count; i++) { expirationTokens.Add(viewDescriptor.ExpirationTokens[i]); } } if (result.Success) { // Populate the viewStartPages list so that _ViewStarts appear in the order the need to be // executed (closest last, furthest first). This is the reverse order in which // ViewHierarchyUtility.GetViewStartLocations returns _ViewStarts. viewStartPages.Insert(0, new ViewLocationCacheItem(result.RazorPageFactory, filePath)); } } return viewStartPages; } private ViewEngineResult CreateViewEngineResult(ViewLocationCacheResult result, string viewName) { if (!result.Success) { return ViewEngineResult.NotFound(viewName, result.SearchedLocations); } var page = result.ViewEntry.PageFactory(); var viewStarts = new IRazorPage[result.ViewStartEntries.Count]; for (var i = 0; i < viewStarts.Length; i++) { var viewStartItem = result.ViewStartEntries[i]; viewStarts[i] = viewStartItem.PageFactory(); } var view = new RazorView(this, _pageActivator, viewStarts, page, _htmlEncoder, _diagnosticListener); return ViewEngineResult.Found(viewName, view); } private static bool IsApplicationRelativePath(string name) { Debug.Assert(!string.IsNullOrEmpty(name)); return name[0] == '~' || name[0] == 'https://www.jb51.net/'; } private static bool IsRelativePath(string name) { Debug.Assert(!string.IsNullOrEmpty(name)); // Though ./ViewName looks like a relative path, framework searches for that view using view locations. return name.EndsWith(ViewExtension, StringComparison.OrdinalIgnoreCase); } } }
我们从用于寻找视图的 FindView 方法开始阅读：