本文原著：牛毅 原文路徑 http://niuyi.github.io/blog/2012/04/06/autofac-by-unit-test/
理解IOC容器請看下圖：
沒有使用IOC容器的情況下:
使用IOC容器的情況下：
去掉IOC容器的情況后：
IOC容器又像一個插座，將電輸送到需要的每一處。需要充電的話，就連接，不需要就不連接，節省資源，不用時時刻刻連上電源了。省電的，哈哈。
使用IOC容器的好處：
1) 可維護性比較好
2) 便於單元測試，調試程序和診斷故障
2) 可復用性好
實現組件之間的解耦，提高程序的靈活性和可維護性
AutoFac使用方法總結:Part I
APR 6TH, 2012 | COMMENTS
AutoFac是.net平台下的IOC容器產品，它可以管理類之間的復雜的依賴關系。在使用方面主要是register和resolve兩類操作。 這篇文章用單元測試的形式列舉了AutoFac的常用使用方法：
注冊部分
使用RegisterType進行注冊
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[Fact] public void can_resolve_myclass() { var builder = new ContainerBuilder(); builder.RegisterType<MyClass>(); IContainer container = builder.Build(); var myClass = container.Resolve<MyClass>(); Assert.NotNull(myClass); }
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注冊為接口
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[Fact] public void register_as_interface() { var builder = new ContainerBuilder(); builder.Register(c => new MyClass()).As<MyInterface>(); IContainer container = builder.Build(); Assert.NotNull(container.Resolve<MyInterface>()); Assert.Throws(typeof (ComponentNotRegisteredException), () => container.Resolve<MyClass>()); }
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使用lambda表達式進行注冊
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[Fact] public void can_register_with_lambda() { var builder = new ContainerBuilder(); builder.Register(c => new MyClass()); IContainer container = builder.Build(); var myClass = container.Resolve<MyClass>(); Assert.NotNull(myClass); }
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帶構造參數的注冊
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[Fact] public void register_with_parameter() { var builder = new ContainerBuilder(); builder.Register(c => new MyParameter()); builder.Register(c => new MyClass(c.Resolve<MyParameter>())); IContainer container = builder.Build(); Assert.NotNull(container.Resolve<MyClass>()); }
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帶屬性賦值的注冊
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[Fact] public void register_with_property() { var builder = new ContainerBuilder(); builder.Register(c => new MyProperty()); builder.Register( c => new MyClass() { Property = c.Resolve<MyProperty>() }); IContainer container = builder.Build(); var myClass = container.Resolve<MyClass>(); Assert.NotNull(myClass); Assert.NotNull(myClass.Property); }
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Autofac分離了類的創建和使用，這樣可以根據輸入參數（NamedParameter）動態的選擇實現類。
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[Fact] public void select_an_implementer_based_on_parameter_value() { var builder = new ContainerBuilder(); builder.Register<IRepository>((c, p) => { var type = p.Named<string>("type"); if (type == "test") { return new TestRepository(); } else { return new DbRepository(); } }).As<IRepository>(); IContainer container = builder.Build(); var repository = container.Resolve<IRepository>(new NamedParameter("type", "test")); Assert.Equal(typeof(TestRepository),repository.GetType()); }
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AufoFac也可以用一個實例來注冊，比如用在單例模式情況下：
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[Fact] public void register_with_instance() { var builder = new ContainerBuilder(); builder.RegisterInstance(MyInstance.Instance).ExternallyOwned(); IContainer container = builder.Build(); var myInstance1 = container.Resolve<MyInstance>(); var myInstance2 = container.Resolve<MyInstance>(); Assert.Equal(myInstance1,myInstance2); }
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注冊open generic類型
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[Fact] public void register_open_generic() { var builder = new ContainerBuilder(); builder.RegisterGeneric(typeof (MyList<>)); IContainer container = builder.Build(); var myIntList = container.Resolve<MyList<int>>(); Assert.NotNull(myIntList); var myStringList = container.Resolve<MyList<string>>(); Assert.NotNull(myStringList); }
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對於同一個接口，后面注冊的實現會覆蓋之前的實現
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[Fact] public void register_order() { var containerBuilder = new ContainerBuilder(); containerBuilder.RegisterType<DbRepository>().As<IRepository>(); containerBuilder.RegisterType<TestRepository>().As<IRepository>(); IContainer container = containerBuilder.Build(); var repository = container.Resolve<IRepository>(); Assert.Equal(typeof(TestRepository), repository.GetType()); }
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如果不想覆蓋的話，可以用PreserveExistingDefaults，這樣會保留原來注冊的實現。
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[Fact] public void register_order_defaults() { var containerBuilder = new ContainerBuilder(); containerBuilder.RegisterType<DbRepository>().As<IRepository>(); containerBuilder.RegisterType<TestRepository>().As<IRepository>().PreserveExistingDefaults(); IContainer container = containerBuilder.Build(); var repository = container.Resolve<IRepository>(); Assert.Equal(typeof (DbRepository), repository.GetType()); }
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可以用Name來區分不同的實現，代替As方法
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[Fact] public void register_with_name() { var containerBuilder = new ContainerBuilder(); containerBuilder.RegisterType<DbRepository>().Named<IRepository>("DB"); containerBuilder.RegisterType<TestRepository>().Named<IRepository>("Test"); IContainer container = containerBuilder.Build(); var dbRepository = container.ResolveNamed<IRepository>("DB"); var testRepository = container.ResolveNamed<IRepository>("Test"); Assert.Equal(typeof(DbRepository), dbRepository.GetType()); Assert.Equal(typeof(TestRepository), testRepository.GetType()); }
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如果一個類有多個構造函數的話，可以在注冊時候選擇不同的構造函數
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[Fact] public void choose_constructors() { var builder = new ContainerBuilder(); builder.RegisterType<MyParameter>(); builder.RegisterType<MyClass>().UsingConstructor(typeof (MyParameter)); IContainer container = builder.Build(); var myClass = container.Resolve<MyClass>(); Assert.NotNull(myClass); }
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AutoFac可以注冊一個Assemble下所有的類，當然，也可以根據類型進行篩選
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[Fact] public void register_assembly() { var builder = new ContainerBuilder(); builder.RegisterAssemblyTypes(Assembly.GetExecutingAssembly()). Where(t => t.Name.EndsWith("Repository")). AsImplementedInterfaces(); IContainer container = builder.Build(); var repository = container.Resolve<IRepository>(); Assert.NotNull(repository); }
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AutoFac使用方法總結:Part II
APR 6TH, 2012 | COMMENTS
事件
AutoFac支持三種事件：OnActivating，OnActivated，OnRelease。OnActivating在注冊組件使用之前會被調用，此時可以替換實現類或者進行一些其他的初始化工作，OnActivated在實例化之后會被調用，OnRelease在組件釋放之后會被調用。
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public class MyEvent : IDisposable { public MyEvent(string input) { Console.WriteLine(input); } public MyEvent() { Console.WriteLine("Init"); } public void Dispose() { Console.WriteLine("Dispose"); } }
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public void test_event() { var builder = new ContainerBuilder(); builder.RegisterType<MyEvent>(). OnActivating(e => e.ReplaceInstance(new MyEvent("input"))). OnActivated(e => Console.WriteLine("OnActivated")). OnRelease(e => Console.WriteLine("OnRelease")); using (IContainer container = builder.Build()) { using (var myEvent = container.Resolve<MyEvent>()) { } } }
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此時的輸出為：
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Init input OnActivated Dispose OnRelease
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利用事件可以在構造對象之后調用對象的方法：
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[Fact] public void call_method_when_init() { var builder = new ContainerBuilder(); builder.RegisterType<MyClassWithMethod>().OnActivating(e => e.Instance.Add(5)); IContainer container = builder.Build(); Assert.Equal(5, container.Resolve<MyClassWithMethod>().Index); } public class MyClassWithMethod { public int Index { get; set; } public void Add(int value) { Index = Index + value; } }
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循環依賴
循環依賴是個比較頭疼的問題，在AutoFac中很多循環依賴的場景不被支持：
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public class ClassA { private readonly ClassB b; public ClassA(ClassB b) { this.b = b; } } public class ClassB { public ClassA A { get; set; } } [Fact] public void circular_dependencies_exception() { var builder = new ContainerBuilder(); builder.Register(c => new ClassB(){A = c.Resolve<ClassA>()}); builder.Register(c => new ClassA(c.Resolve<ClassB>())); IContainer container = builder.Build(); Assert.Throws(typeof(DependencyResolutionException), ()=>container.Resolve<ClassA>()); }
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可以部分的解決這種循環依賴的問題，前提是ClassA和ClassB的生命周期不能都是InstancePerDependency
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[Fact] public void circular_dependencies_ok() { var builder = new ContainerBuilder(); builder.RegisterType<ClassB>(). PropertiesAutowired(PropertyWiringFlags.AllowCircularDependencies).SingleInstance(); builder.Register(c => new ClassA(c.Resolve<ClassB>())); IContainer container = builder.Build(); Assert.NotNull(container.Resolve<ClassA>()); Assert.NotNull(container.Resolve<ClassB>()); Assert.NotNull(container.Resolve<ClassB>().A); }
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AutoFac使用方法總結:Part III
APR 6TH, 2012 | COMMENTS
生命周期
AutoFac中的生命周期概念非常重要，AutoFac也提供了強大的生命周期管理的能力。
AutoFac定義了三種生命周期：
Per Dependency
Single Instance
Per Lifetime Scope
Per Dependency為默認的生命周期，也被稱為’transient’或’factory’，其實就是每次請求都創建一個新的對象
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[Fact] public void per_dependency() { var builder = new ContainerBuilder(); builder.RegisterType<MyClass>().InstancePerDependency(); IContainer container = builder.Build(); var myClass1 = container.Resolve<MyClass>(); var myClass2 = container.Resolve<MyClass>(); Assert.NotEqual(myClass1,myClass2); }
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Single Instance也很好理解，就是每次都用同一個對象
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[Fact] public void single_instance() { var builder = new ContainerBuilder(); builder.RegisterType<MyClass>().SingleInstance(); IContainer container = builder.Build(); var myClass1 = container.Resolve<MyClass>(); var myClass2 = container.Resolve<MyClass>(); Assert.Equal(myClass1,myClass2); }
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Per Lifetime Scope，同一個Lifetime生成的對象是同一個實例
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[Fact] public void per_lifetime_scope() { var builder = new ContainerBuilder(); builder.RegisterType<MyClass>().InstancePerLifetimeScope(); IContainer container = builder.Build(); var myClass1 = container.Resolve<MyClass>(); var myClass2 = container.Resolve<MyClass>(); ILifetimeScope inner = container.BeginLifetimeScope(); var myClass3 = inner.Resolve<MyClass>(); var myClass4 = inner.Resolve<MyClass>(); Assert.Equal(myClass1,myClass2); Assert.NotEqual(myClass2,myClass3); Assert.Equal(myClass3,myClass4); }
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[Fact] public void life_time_and_dispose() { var builder = new ContainerBuilder(); builder.RegisterType<Disposable>(); using (IContainer container = builder.Build()) { var outInstance = container.Resolve<Disposable>(new NamedParameter("name", "out")); using(var inner = container.BeginLifetimeScope()) { var inInstance = container.Resolve<Disposable>(new NamedParameter("name", "in")); }//inInstance dispose here }//out dispose here }
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