(五)学习了解OrchardCore笔记——灵魂中间件ModularTenantContainerMiddleware的第一行②模块的功能部分
在(三)的时候已经说到模块集合用ForEachAsync的扩展方法分配多个任务，把每个modules的ManifestInfo分析出来的功能加入ConcurrentDictionary。我们先看看这个扩展方法：
public static class EnumerableExtensions { public static Task ForEachAsync<T>(this IEnumerable<T> source, Func<T, Task> body) { var partitionCount = System.Environment.ProcessorCount; return Task.WhenAll( from partition in Partitioner.Create(source).GetPartitions(partitionCount) select Task.Run(async delegate { using (partition) { while (partition.MoveNext()) { await body(partition.Current); } } })); } }
这个查下msdn就非常简单明了，partitionCount获取可用逻辑处理器的数量(网上也有说是一组逻辑处理器的数量，一组的区别是有的服务器cpu是多组核心构成的，clr只能在一组逻辑处理器运行？也有人说现在已经可以运行在该服务器所有逻辑处理器上了，这点我不清楚，因为我没有这么多核心的处理器可以测试，这里当作所有逻辑处理器吧)。然后Partitioner.Create(source)就是把模块集合创建成可排序的程序分区，GetPartitions(partitionCount)就是按逻辑处理器的数量分区，然后开始按分区执行任务，看看partition.MoveNext()就是每个分区都是一个接着一个执行到最后一个集合的元素(Task.WhenAll和Task.Run这个不用说估计大家都懂，不懂自己msdn)，partition.Current就是当前位置的元素。body就是委托，因此可以清晰的知道ForEachAsync就是把modules集合按逻辑处理器分区然后迭代执行委托，天啊，我只会foreach，这种多线程操作我也是第一次见。
返回ExtensionManager类继续看看ForEachAsync这部分代码
// Load all extensions in parallel await modules.ForEachAsync((module) => { if (!module.ModuleInfo.Exists) { return Task.CompletedTask; } var manifestInfo = new ManifestInfo(module.ModuleInfo); var extensionInfo = new ExtensionInfo(module.SubPath, manifestInfo, (mi, ei) => { return _featuresProvider.GetFeatures(ei, mi); }); var entry = new ExtensionEntry { ExtensionInfo = extensionInfo, Assembly = module.Assembly, ExportedTypes = module.Assembly.ExportedTypes }; loadedExtensions.TryAdd(module.Name, entry); return Task.CompletedTask; });
每个modules集合的元素都执行一遍ForEachAsync里面的委托(我还是喜欢c里面指针函数的叫法，因为明显就是个函数吗)。看看这个函数不对是委托，传入参数就是具体的某一个module，先判断module.ModuleInfo是否存在，之前篇幅没说这个module.ModuleInfo其实就是每个模块项目(包括主题项目)里面的Manifest.cs文件映射到类，看看Module的构造函数就很清楚了(在(三)里面Application实例化中第二个参数里面GetModules()添加Module的时候)。也就是说以后自定义模块必须包含这个文件，不然不会加载进来。接下来就实例化该模块的扩展信息类extensionInfo，这个类很简单，我们看看ExtensionInfo的代码：
public class ExtensionInfo : IExtensionInfo { public ExtensionInfo( string subPath, IManifestInfo manifestInfo, Func<IManifestInfo, IExtensionInfo, IEnumerable<IFeatureInfo>> features) { SubPath = subPath; Manifest = manifestInfo; Features = features(manifestInfo, this); } public string Id => Manifest.ModuleInfo.Id; public string SubPath { get; } public IManifestInfo Manifest { get; } public IEnumerable<IFeatureInfo> Features { get; } public bool Exists => Manifest.Exists; }
里面主要几个属性((三)里没追踪Modules自己追踪下很清楚这些属性的值是什么)。构造函数传入的三个参数也很明了就是实例化给属性赋值。1、SubPath模块的路径，自己点下很清晰就是Areas/模块名，这个很属性吧，没错，跟asp.net core的区域一样。2、Manifest模块的Manifest.cs文件反射出的类。3、调用这个委托给功能集合赋值。我们看看这个委托实现的代码(跟ExtensionManager同个目录下有个Features目录的FeaturesProvider类)：
public class FeaturesProvider : IFeaturesProvider { public const string FeatureProviderCacheKey = "FeatureProvider:Features"; private readonly IEnumerable<IFeatureBuilderEvents> _featureBuilderEvents; public FeaturesProvider(IEnumerable<IFeatureBuilderEvents> featureBuilderEvents) { _featureBuilderEvents = featureBuilderEvents; } public IEnumerable<IFeatureInfo> GetFeatures( IExtensionInfo extensionInfo, IManifestInfo manifestInfo) { var featuresInfos = new List<IFeatureInfo>(); // Features and Dependencies live within this section var features = manifestInfo.ModuleInfo.Features.ToList(); if (features.Count > 0) { foreach (var feature in features) { if (String.IsNullOrWhiteSpace(feature.Id)) { throw new ArgumentException( $"A feature is missing a mandatory 'Id' property in the Module '{extensionInfo.Id}'"); } var featureId = feature.Id; var featureName = feature.Name ?? feature.Id; var featureDependencyIds = feature.Dependencies .Select(e => e.Trim()).ToArray(); if (!int.TryParse(feature.Priority ?? manifestInfo.ModuleInfo.Priority, out int featurePriority)) { featurePriority = 0; } var featureCategory = feature.Category ?? manifestInfo.ModuleInfo.Category; var featureDescription = feature.Description ?? manifestInfo.ModuleInfo.Description; var featureDefaultTenantOnly = feature.DefaultTenantOnly; var featureIsAlwaysEnabled = feature.IsAlwaysEnabled; var context = new FeatureBuildingContext { FeatureId = featureId, FeatureName = featureName, Category = featureCategory, Description = featureDescription, ExtensionInfo = extensionInfo, ManifestInfo = manifestInfo, Priority = featurePriority, FeatureDependencyIds = featureDependencyIds, DefaultTenantOnly = featureDefaultTenantOnly, IsAlwaysEnabled = featureIsAlwaysEnabled }; foreach (var builder in _featureBuilderEvents) { builder.Building(context); } var featureInfo = new FeatureInfo( featureId, featureName, featurePriority, featureCategory, featureDescription, extensionInfo, featureDependencyIds, featureDefaultTenantOnly, featureIsAlwaysEnabled); foreach (var builder in _featureBuilderEvents) { builder.Built(featureInfo); } featuresInfos.Add(featureInfo); } } else { // The Extension has only one feature, itself, and that can have dependencies var featureId = extensionInfo.Id; var featureName = manifestInfo.Name; var featureDependencyIds = manifestInfo.ModuleInfo.Dependencies .Select(e => e.Trim()).ToArray(); if (!int.TryParse(manifestInfo.ModuleInfo.Priority, out int featurePriority)) { featurePriority = 0; } var featureCategory = manifestInfo.ModuleInfo.Category; var featureDescription = manifestInfo.ModuleInfo.Description; var featureDefaultTenantOnly = manifestInfo.ModuleInfo.DefaultTenantOnly; var featureIsAlwaysEnabled = manifestInfo.ModuleInfo.IsAlwaysEnabled; var context = new FeatureBuildingContext { FeatureId = featureId, FeatureName = featureName, Category = featureCategory, Description = featureDescription, ExtensionInfo = extensionInfo, ManifestInfo = manifestInfo, Priority = featurePriority, FeatureDependencyIds = featureDependencyIds, DefaultTenantOnly = featureDefaultTenantOnly, IsAlwaysEnabled = featureIsAlwaysEnabled }; foreach (var builder in _featureBuilderEvents) { builder.Building(context); } var featureInfo = new FeatureInfo( context.FeatureId, context.FeatureName, context.Priority, context.Category, context.Description, context.ExtensionInfo, context.FeatureDependencyIds, context.DefaultTenantOnly, context.IsAlwaysEnabled); foreach (var builder in _featureBuilderEvents) { builder.Built(featureInfo); } featuresInfos.Add(featureInfo); } return featuresInfos; } }
看起来有点长，其实没啥说的，基本都在赋值，构造函数通过依赖注入解决，略过。直接看看委托的方法GetFeatures(IExtensionInfo extensionInfo,IManifestInfo manifestInfo)，两个参数就是刚刚那个扩展信息和对应的mainfest.cs所反射的类。创建要返回的功能列表信息集合var featuresInfos = new List<IFeatureInfo>()。然后获取该模块依赖的功能集合var features = manifestInfo.ModuleInfo.Features.ToList()，官网也说了一个模块可以有0到多个功能，具体就是Manifest.cs文件有没多个assembly: Feature，具体代码0个和多个并没有多大区别，你可以发现多个了用foreach把每个功能加入集合，0个就用扩展信息填充功能然后加入集合返回。这些没啥问题，然后之前好像注入了什么featureBuilderEvents在这里居然有两个方法Building和Built，它们实现的类是ThemeFeatureBuilderEvents(继承FeatureBuilderEvents，依赖注入不说也懂，直接找实现就对了，我最怕Events了，我最不了解事件，说是委托的封装，委托我直接理解成指针函数，事件这个概念我还没想好代替的说辞，其实我都是简单的理解成多个委托，毕竟事件和委托的区别就是事件可以有多个方法嘛，不对多个委托，我c#都是自学，这些概念可能表述不清楚，上学科班只教了c和java里面都没这种概念，我是计算机系但是非软件专业而是网络专业，见谅)。重写了方法Building，就是提取出主题啊(判断是否是主题)，(四)这篇说过，模块包含三个解决方案文件夹里的项目：普通模块、cms模块和主题模块(可能上篇表述不一样)。下面代码很明显就是有基础主题就修改下：
public class ThemeFeatureBuilderEvents : FeatureBuilderEvents { public override void Building(FeatureBuildingContext context) { var moduleInfo = context.ExtensionInfo.Manifest.ModuleInfo; if (moduleInfo is ThemeAttribute || (moduleInfo is ModuleMarkerAttribute && moduleInfo.Type.Equals("Theme", StringComparison.OrdinalIgnoreCase))) { var extensionInfo = new ThemeExtensionInfo(context.ExtensionInfo); if (extensionInfo.HasBaseTheme()) { context.FeatureDependencyIds = context .FeatureDependencyIds .Concat(new[] { extensionInfo.BaseTheme }) .ToArray(); } context.ExtensionInfo = extensionInfo; } } }
感觉第(四)篇了解过后没啥说的，后面直接跟踪就好了，是我的角度不对？怪不得别人都从架构说起，我从asp.net core按流程说中间少了点什么，有点不连贯，老是得去补充点什么，越说越乱，被我弄乱的感觉还不如直接自己追踪下源码？我看看能不能努力写到下个中间件。要我从架构上说我办不到啊，我连画uml的软件都不知道有哪些，后面学学看。
