扒一扒asp.net core mvc控制器的寻找流程

不太会排版,大家将就看吧扒一扒asp.net core mvc控制器的寻找流程 .

asp.net core mvc和asp.net mvc中都有一个比较有意思的而又被大家容易忽略的功能,控制器可以写在非Web程序集中,比如Web程序集:"MyWeb",引用程序集"B.bll",你可以将所有的控制器写在"B.bll"程序集里面.mvc框架仍然可以寻找到这个控制器.

仔细想一想,mvc框架启动的时候寻找过程:1.找到所有包含控制器的程序集;2.反射找到所有控制器类型;3.反射找到所有的action;4.缓存这些controller与action.

那么有意思的就是第一步"找到所有包含控制器的程序集",一开始我认为是扫描当前应用程序域已加载的程序集,然后反射判断存不存在控制器类型.单如果一个程序有上千个程序集,那么反射无疑是一种灾难,mvc的启动也没这么慢啊,怀着好奇的心,这里就扒一扒官方的实现原理(asp.net mvc源码没去看,但原理估计差不多,这里就扒asp.net core mvc).

这里建议大家先了解下 asp.net core mvc的启动流程:http://www.cnblogs.com/savorboard/p/aspnetcore-mvc-startup.html.

action的匹配:http://www.cnblogs.com/savorboard/p/aspnetcore-mvc-routing-action.html

这里引用杨晓东博客中的图片:

扒一扒asp.net core mvc控制器的寻找流程

1.AddMvcCore,mvc核心启动代码:

        public static IMvcCoreBuilder AddMvcCore(this IServiceCollection services)
        {
            if (services == null)
            {
                throw new ArgumentNullException(nameof(services));
            }
            //获取ApplicationPartManager管理类,该类保存了ApplicationPart集合,而ApplicationPart最重要的子类AssemblyPart记录了程序集信息,另外PopulateFeature用于填充各种功能
            var partManager = GetApplicationPartManager(services);
            services.TryAddSingleton(partManager);

            ConfigureDefaultFeatureProviders(partManager);
            ConfigureDefaultServices(services);
            AddMvcCoreServices(services);

            var builder = new MvcCoreBuilder(services, partManager);

            return builder;
        }

ApplicationPartManager:

    /// <summary>
    /// Manages the parts and features of an MVC application.
    /// </summary>
    public class ApplicationPartManager
    {
        /// <summary>
        /// Gets the list of <see cref="IApplicationFeatureProvider"/>s.
        /// </summary>
        public IList<IApplicationFeatureProvider> FeatureProviders { get; } =
            new List<IApplicationFeatureProvider>();

        /// <summary>
        /// Gets the list of <see cref="ApplicationPart"/>s.
        /// </summary>
        public IList<ApplicationPart> ApplicationParts { get; } =
            new List<ApplicationPart>();

        /// <summary>
        /// Populates the given <paramref name="feature"/> using the list of
        /// <see cref="IApplicationFeatureProvider{TFeature}"/>s configured on the
        /// <see cref="ApplicationPartManager"/>.
        /// </summary>
        /// <typeparam name="TFeature">The type of the feature.</typeparam>
        /// <param name="feature">The feature instance to populate.</param>
        public void PopulateFeature<TFeature>(TFeature feature)
        {
            if (feature == null)
            {
                throw new ArgumentNullException(nameof(feature));
            }

            foreach (var provider in FeatureProviders.OfType<IApplicationFeatureProvider<TFeature>>())
            {
                provider.PopulateFeature(ApplicationParts, feature);
            }
        }
    }

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