IOC容器特性注入第一篇：程序集反射查找

学习kooboo的框架发现它的注入容器方法比较特别，同样是利用MVC的注入点，但它是查找网站下面bin所有的DLL利用反射查找特性找到对应的服务注入到容器。

这样的好处很简单：完全可以不用关心IOC容器是Ninject还是autofac 或者其它什么容器。 只要写上特性标记，再把对应的DLL拷贝到BIN下面，网站一启动就会自动注入到容器中。彻底进行解耦。

它的IOC注入步骤先后顺序：

1.程序集反射查找

2.IOC容器引擎初始化

3.利用特性注入IOC容器

4.MVC注入点注入

因为本人比较笨，理解东西比较差强人意，所以将以7篇文章分别介绍各个模块加强自己的理解：

IOC容器特性注入第一篇：程序集反射查找

IOC容器特性注入第二篇：初始引擎查找对应的IOC容器

IOC容器特性注入第三篇：Attribute封装

IOC容器特性注入第四篇：容器初始化

IOC容器特性注入第五篇：查找(Attribute)特性注入

IOC容器特性注入第六篇：利用MVC注入点，把容器启动

IOC容器特性注入第七篇：请求上下文作用域

源代码，我放在最后一篇，大家可以去下载。

我首先介绍下如何对网站BIN下面的DLL进行反射查找：

 kooboo的程序集反射查找类就是Nop的三个封装类，分别是：

1.接口(ITypeFinder)：

    public interface ITypeFinder {
        IList<Assembly> GetAssemblies();

        IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType<T>(bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType<T>(IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true);

        IEnumerable<Type> FindClassesOfType<T, TAssemblyAttribute>(bool onlyConcreteClasses = true) where TAssemblyAttribute : Attribute;

        IEnumerable<Assembly> FindAssembliesWithAttribute<T>();

        IEnumerable<Assembly> FindAssembliesWithAttribute<T>(IEnumerable<Assembly> assemblies);

        IEnumerable<Assembly> FindAssembliesWithAttribute<T>(DirectoryInfo assemblyPath);
    }

2.应用程序实现类(AppDomainTypeFinder)：

public class AppDomainTypeFinder : ITypeFinder {
        #region Private Fields

        private bool loadAppDomainAssemblies = true;

        private string assemblySkipLoadingPattern = "^System|^mscorlib|^Microsoft|^CppCodeProvider|^VJSharpCodeProvider|^WebDev|^Castle|^Iesi|^log4net|^NHibernate|^nunit|^TestDriven|^MbUnit|^Rhino|^QuickGraph|^TestFu|^Telerik|^ComponentArt|^MvcContrib|^AjaxControlToolkit|^Antlr3|^Remotion|^Recaptcha|^DotNetOpenAuth,";

        private string assemblyRestrictToLoadingPattern = ".*";
        private IList<string> assemblyNames = new List<string>();

        #endregion

        #region Constructors

        /// <summary>Creates a new instance of the AppDomainTypeFinder.</summary>
        public AppDomainTypeFinder() {
        }

        #endregion

        #region Properties

        /// <summary>The app domain to look for types in.</summary>
        public virtual AppDomain App {
            get { return AppDomain.CurrentDomain; }
        }

        /// <summary>Gets or sets wether app should iterate assemblies in the app domain when loading types. Loading patterns are applied when loading these assemblies.</summary>
        public bool LoadAppDomainAssemblies {
            get { return loadAppDomainAssemblies; }
            set { loadAppDomainAssemblies = value; }
        }

        /// <summary>Gets or sets assemblies loaded a startup in addition to those loaded in the AppDomain.</summary>
        public IList<string> AssemblyNames {
            get { return assemblyNames; }
            set { assemblyNames = value; }
        }

        /// <summary>Gets the pattern for dlls that we know don't need to be investigated.</summary>
        public string AssemblySkipLoadingPattern {
            get { return assemblySkipLoadingPattern; }
            set { assemblySkipLoadingPattern = value; }
        }

        /// <summary>Gets or sets the pattern for dll that will be investigated. For ease of use this defaults to match all but to increase performance you might want to configure a pattern that includes assemblies and your own.</summary>
        /// <remarks>If you change this so that assemblies arn't investigated (e.g. by not including something like "^MTA|..." you may break core functionality.</remarks>
        public string AssemblyRestrictToLoadingPattern {
            get { return assemblyRestrictToLoadingPattern; }
            set { assemblyRestrictToLoadingPattern = value; }
        }

        #endregion

        #region Internal Attributed Assembly class

        private class AttributedAssembly {
            internal Assembly Assembly { get; set; }
            internal Type PluginAttributeType { get; set; }
        }

        #endregion

        #region ITypeFinder

        public IEnumerable<Type> FindClassesOfType<T>(bool onlyConcreteClasses = true) {
            return FindClassesOfType(typeof(T), onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, bool onlyConcreteClasses = true) {
            return FindClassesOfType(assignTypeFrom, GetAssemblies(), onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType<T>(IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true) {
            return FindClassesOfType(typeof(T), assemblies, onlyConcreteClasses);
        }

        public IEnumerable<Type> FindClassesOfType(Type assignTypeFrom, IEnumerable<Assembly> assemblies, bool onlyConcreteClasses = true) {
            var result = new List<Type>();
            try {
                foreach (var a in assemblies) {
                    foreach (var t in a.GetTypes()) {
                        if (assignTypeFrom.IsAssignableFrom(t) || (assignTypeFrom.IsGenericTypeDefinition && DoesTypeImplementOpenGeneric(t, assignTypeFrom))) {
                            if (!t.IsInterface) {
                                if (onlyConcreteClasses) {
                                    if (t.IsClass && !t.IsAbstract) {
                                        result.Add(t);
                                    }
                                } else {
                                    result.Add(t);
                                }
                            }
                        }
                    }
                }
            } catch (ReflectionTypeLoadException ex) {
                var msg = string.Empty;
                foreach (var e in ex.LoaderExceptions)
                    msg += e.Message + Environment.NewLine;

                var fail = new Exception(msg, ex);
                Debug.WriteLine(fail.Message, fail);

                throw fail;
            }
            return result;
        }

        public IEnumerable<Type> FindClassesOfType<T, TAssemblyAttribute>(bool onlyConcreteClasses = true) where TAssemblyAttribute : Attribute {
            var found = FindAssembliesWithAttribute<TAssemblyAttribute>();
            return FindClassesOfType<T>(found, onlyConcreteClasses);
        }

        public IEnumerable<Assembly> FindAssembliesWithAttribute<T>() {
            return FindAssembliesWithAttribute<T>(GetAssemblies());
        }

        /// <summary>
        /// Caches attributed assembly information so they don't have to be re-read
        /// </summary>
        private readonly List<AttributedAssembly> _attributedAssemblies = new List<AttributedAssembly>();

        /// <summary>
        /// Caches the assembly attributes that have been searched for
        /// </summary>
        private readonly List<Type> _assemblyAttributesSearched = new List<Type>();

        public IEnumerable<Assembly> FindAssembliesWithAttribute<T>(IEnumerable<Assembly> assemblies) {
            //check if we've already searched this assembly);)
            if (!_assemblyAttributesSearched.Contains(typeof(T))) {
                var foundAssemblies = (from assembly in assemblies
                                       let customAttributes = assembly.GetCustomAttributes(typeof(T), false)
                                       where customAttributes.Any()
                                       select assembly).ToList();
                //now update the cache
                _assemblyAttributesSearched.Add(typeof(T));
                foreach (var a in foundAssemblies) {
                    _attributedAssemblies.Add(new AttributedAssembly { Assembly = a, PluginAttributeType = typeof(T) });
                }
            }

            //We must do a ToList() here because it is required to be serializable when using other app domains.
            return _attributedAssemblies
                .Where(x => x.PluginAttributeType.Equals(typeof(T)))
                .Select(x => x.Assembly)
                .ToList();
        }

        public IEnumerable<Assembly> FindAssembliesWithAttribute<T>(DirectoryInfo assemblyPath) {
            var assemblies = (from f in Directory.GetFiles(assemblyPath.FullName, "*.dll")
                              select Assembly.LoadFrom(f)
                                  into assembly
                                  let customAttributes = assembly.GetCustomAttributes(typeof(T), false)
                                  where customAttributes.Any()
                                  select assembly).ToList();
            return FindAssembliesWithAttribute<T>(assemblies);
        }

        /// <summary>Gets tne assemblies related to the current implementation.</summary>
        /// <returns>A list of assemblies that should be loaded by the factory.</returns>
        public virtual IList<Assembly> GetAssemblies() {
            var addedAssemblyNames = new List<string>();
            var assemblies = new List<Assembly>();

            if (LoadAppDomainAssemblies)
                AddAssembliesInAppDomain(addedAssemblyNames, assemblies);
            AddConfiguredAssemblies(addedAssemblyNames, assemblies);

            return assemblies;
        }

        #endregion

        /// <summary>Iterates all assemblies in the AppDomain and if it's name matches the configured patterns add it to our list.</summary>
        /// <param name="addedAssemblyNames"></param>
        /// <param name="assemblies"></param>
        private void AddAssembliesInAppDomain(List<string> addedAssemblyNames, List<Assembly> assemblies) {
            foreach (Assembly assembly in AppDomain.CurrentDomain.GetAssemblies()) {
                if (Matches(assembly.FullName)) {
                    if (!addedAssemblyNames.Contains(assembly.FullName)) {
                        assemblies.Add(assembly);
                        addedAssemblyNames.Add(assembly.FullName);
                    }
                }
            }
        }

        /// <summary>Adds specificly configured assemblies.</summary>
        protected virtual void AddConfiguredAssemblies(List<string> addedAssemblyNames, List<Assembly> assemblies) {
            foreach (string assemblyName in AssemblyNames) {
                Assembly assembly = Assembly.Load(assemblyName);
                if (!addedAssemblyNames.Contains(assembly.FullName)) {
                    assemblies.Add(assembly);
                    addedAssemblyNames.Add(assembly.FullName);
                }
            }
        }

        /// <summary>Check if a dll is one of the shipped dlls that we know don't need to be investigated.</summary>
        /// <param name="assemblyFullName">The name of the assembly to check.</param>
        /// <returns>True if the assembly should be loaded into app.</returns>
        public virtual bool Matches(string assemblyFullName) {
            return !Matches(assemblyFullName, AssemblySkipLoadingPattern)
                   && Matches(assemblyFullName, AssemblyRestrictToLoadingPattern);
        }

        /// <summary>Check if a dll is one of the shipped dlls that we know don't need to be investigated.</summary>
        /// <param name="assemblyFullName">The assembly name to match.</param>
        /// <param name="pattern">The regular expression pattern to match against the assembly name.</param>
        /// <returns>True if the pattern matches the assembly name.</returns>
        protected virtual bool Matches(string assemblyFullName, string pattern) {
            return Regex.IsMatch(assemblyFullName, pattern, RegexOptions.IgnoreCase | RegexOptions.Compiled);
        }

        /// <summary>Makes sure matching assemblies in the supplied folder are loaded in the app domain.</summary>
        /// <param name="directoryPath">The physical path to a directory containing dlls to load in the app domain.</param>
        protected virtual void LoadMatchingAssemblies(string directoryPath) {
            var loadedAssemblyNames = new List<string>();
            foreach (Assembly a in GetAssemblies()) {
                loadedAssemblyNames.Add(a.FullName);
            }

            if (!Directory.Exists(directoryPath)) {
                return;
            }

            foreach (string dllPath in Directory.GetFiles(directoryPath, "*.dll")) {
                try {
                    var an = AssemblyName.GetAssemblyName(dllPath);
                    if (Matches(an.FullName) && !loadedAssemblyNames.Contains(an.FullName)) {
                        App.Load(an);
                    }

                    //old loading stuff
                    //Assembly a = Assembly.ReflectionOnlyLoadFrom(dllPath);
                    //if (Matches(a.FullName) && !loadedAssemblyNames.Contains(a.FullName))
                    //{
                    //    App.Load(a.FullName);
                    //}
                } catch (BadImageFormatException ex) {
                    Trace.TraceError(ex.ToString());
                }
            }
        }

        protected virtual bool DoesTypeImplementOpenGeneric(Type type, Type openGeneric) {
            try {
                var genericTypeDefinition = openGeneric.GetGenericTypeDefinition();
                foreach (var implementedInterface in type.FindInterfaces((objType, objCriteria) => true, null)) {
                    if (!implementedInterface.IsGenericType)
                        continue;

                    var isMatch = genericTypeDefinition.IsAssignableFrom(implementedInterface.GetGenericTypeDefinition());
                    return isMatch;
                }
                return false;
            } catch {
                return false;
            }
        }

    }

3.web应用程序继承App作用域类(WebAppTypeFinder)：

public class WebAppTypeFinder : AppDomainTypeFinder {
        #region Fields

        private bool _ensureBinFolderAssembliesLoaded = true;
        private bool _binFolderAssembliesLoaded = false;

        #endregion

        #region Ctor

        public WebAppTypeFinder() {
            this._ensureBinFolderAssembliesLoaded = true;
        }

        #endregion

        #region Properties

        /// <summary>
        /// Gets or sets wether assemblies in the bin folder of the web application should be specificly checked for beeing loaded on application load. This is need in situations where plugins need to be loaded in the AppDomain after the application been reloaded.
        /// </summary>
        public bool EnsureBinFolderAssembliesLoaded {
            get { return _ensureBinFolderAssembliesLoaded; }
            set { _ensureBinFolderAssembliesLoaded = value; }
        }

        #endregion

        #region Methods

        /// <summary>
        /// Gets a physical disk path of \Bin directory
        /// </summary>
        /// <returns>The physical path. E.g. "c:\inetpub\wwwroot\bin"</returns>
        public virtual string GetBinDirectory() {
            if (HostingEnvironment.IsHosted) {
                //hosted
                return HttpRuntime.BinDirectory;
            } else {
                //not hosted. For example, run either in unit tests
                return AppDomain.CurrentDomain.BaseDirectory;
            }
        }


        public override IList<Assembly> GetAssemblies() {
            if (this.EnsureBinFolderAssembliesLoaded && !_binFolderAssembliesLoaded) {
                _binFolderAssembliesLoaded = true;
                string binPath = GetBinDirectory();
                //binPath = _webHelper.MapPath("~/bin");
                LoadMatchingAssemblies(binPath);
            }

            return base.GetAssemblies();
        }
        #endregion
    }

WebAppTypeFinder 这个类就可以对网站下面BIN文件夹所有的DLL文件进行反射查找程序集，可以根据类型 也可以跟特性查找，总之性能不错，大家可以拷贝代码 进行测试。

下一篇：

IOC容器特性注入第二篇：初始引擎查找对应的IOC容器