IOC Of Ninject Base On ASP.NET MVC
說在之前的話
IOC的概念相信大家比較熟悉了,習慣性稱之為依賴註入或控制反轉,園子裏對基於MVC平臺IOC設計模式已經相當多了,但大家都只知道應該怎麽應用一個IOC模式,比如Ninject, Unity等常用框架,並不清楚為什麽要用它,它們之間有什麽區別,換句話說在實際應用中的橫向對比的文章比較少,本文旨在拋磚引玉,歡迎大家討論
Ninject模式實現
VS工具提供了很方便的ninject模式引入,新建一個asp.net mvc項目後,執行幾行命令就即可
1.添加Ninject。工具-->Nuget程序包管理器-->程序包管理器控制臺,輸入下面的命令:
Install-Package Ninject -version 3.0.1.10 Install-Package Ninject.Web.Common -version 3.0.0.7 Install-Package Ninject.MVC3 -Version 3.0.0.6
分別引用了
Minject
Ninject.Web.Common
Ninject.Web.MVC
Ninject模式下,有兩種常用的方式實現,一種是通過Activitor激活Controller的方式,另一種方式MVC5推薦的DependencyResolver方式
首先做好準備工作,假設有一個Employee實體類
public class Employee { [Display(Name="ID")] public string Id { get; private set; } [Display(Name = "姓名")]public string Name { get; private set; } [Display(Name = "性別")] public string Gender { get; private set; } [Display(Name = "出生日期")] [DataType(DataType.Date)] public DateTime BirthDate { get; private set; } [Display(Name = "部門")] public string Department { get; private set; } public Employee(string id, string name, string gender, DateTime birthDate, string department) { this.Id = id; this.Name = name; this.Gender = gender; this.BirthDate = birthDate; this.Department = department; } }
對實現類提供的操作服務
public interface IEmployeeRepository { IEnumerable<Employee> GetEmployees(string id = ""); }
添加對服務的實現
public class EmployeeRepository: IEmployeeRepository { private static IList<Employee> employees; static EmployeeRepository() { employees = new List<Employee>(); employees.Add(new Employee(Guid.NewGuid().ToString(), "Employee1", "男", new DateTime(1987, 8, 24), "銷售部")); employees.Add(new Employee(Guid.NewGuid().ToString(), "Employee2", "男", new DateTime(1991, 7, 10), "人事部")); employees.Add(new Employee(Guid.NewGuid().ToString(), "Employee3", "女", new DateTime(1993, 9, 21), "財務部")); } public IEnumerable<Employee> GetEmployees(string id = "") { return employees.Where(e => e.Id == id || string.IsNullOrEmpty(id) || id == "*"); } }
1.看看最新的DependencyResolver方式的實現,新建類 NinjectDependencyResolver 來實現IDependencyResolver的GetService和GetSerivices兩個接口,
註意這裏的Bind的方法,這裏是為Controller註冊Service的核心代碼,所有Controller中以來的Ninject接口服務都在這裏註冊(接口與實現分離,Ninject托管)
public class NinjectDependencyResolver : IDependencyResolver { private IKernel kernel; public NinjectDependencyResolver() { kernel = new StandardKernel(); Bind(); } public NinjectDependencyResolver(IKernel kernelParam) { kernel = kernelParam; Bind(); } public object GetService(Type serviceType) { return kernel.TryGet(serviceType); } public IEnumerable<object> GetServices(Type serviceType) { return kernel.GetAll(serviceType); } private void Bind() { this.kernel.Bind<IEmployeeRepository>().To<EmployeeRepository>(); }
上面已經註冊了服務,現在需要把註冊信息告訴Controller的Builder工廠;MVC5把這個工作已經自動化了,當最上面引入Ninject.Web.Common的時候,已經在App_Start文件夾下自動生成了NinjectWebCommon,註意RegisterServices方法需要我們主動將上面已經寫好的註冊類NinjectDependencyResolver初始化給Mvc.DependencyResolver對象,大家不難發現這裏是對當前程序的全局設置,事實上NinjectWebCommon的Start方法比Global中Application_Start方法更早的執行,已便對整個應用程序做好初始化
public static class NinjectWebCommon { private static readonly Bootstrapper bootstrapper = new Bootstrapper(); /// <summary> /// Starts the application /// </summary> public static void Start() { DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule)); DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule)); bootstrapper.Initialize(CreateKernel); } /// <summary> /// Stops the application. /// </summary> public static void Stop() { bootstrapper.ShutDown(); } /// <summary> /// Creates the kernel that will manage your application. /// </summary> /// <returns>The created kernel.</returns> private static IKernel CreateKernel() { var kernel = new StandardKernel(); kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel); kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>(); RegisterServices(kernel); return kernel; } /// <summary> /// Load your modules or register your services here! /// </summary> /// <param name="kernel">The kernel.</param> private static void RegisterServices(IKernel kernel) { System.Web.Mvc.DependencyResolver.SetResolver(new NinjectDependencyResolver(kernel)); } }
到此Ninject已經引入完成了,怎麽使用呢
下面添加一個對Employee操作的Controller, 聲明一個IEmployeeRepository服務,註意這裏是接口,在上面打上[Inject]標記後,在Action方法中就可以隨意使用Employee服務了。可能有人疑惑這裏的IEmployeeRepository沒實例化如何就能使用,其實上面實現的RegisterServices方法中,已經對ControllerBuilder的初始化了註冊信息,所有實現Controller的子類在實例化時根據[Inject]標記查找註冊信息中的實現類進行初始化服務,在Action中引用的已經是實例化好的服務實體了
public class EmployeeController : Controller { [Inject] public IEmployeeRepository Repository { get; set; } public ActionResult Index() { var employees = this.Repository.GetEmployees(); return View(employees); } public ActionResult Detail(string id) { Employee employee = this.Repository.GetEmployees(id).FirstOrDefault(); if (null == employee) { throw new HttpException(404, string.Format("ID為{0}的員工不存在", id)); } return View(employee); } }
讀到這算是知其然了,感覺很麻煩,為什麽不直接在controller裏new一個EmployeeRepository,接口都省了,想到這點說明你很勤於思考,回答這點需要說下為什麽要引入Ninject,或者說IOC有什麽好處,多做了那麽多復雜的動作,好處呢
1. 這裏托管給Jinject的服務實例會根據訪問量最大限度的節約實例創建,如果省了這些,我們不得不在每個controller中保留要依賴的服務對象占用資源
2.controller中並沒有直接對服務的實現類依賴,而是引用的接口,也就是說,controller開發者不需要關心服務是否已經現實,只在接口已經聲明就可以開發,這即是實現當下最流行的敏捷開發的基礎,後端服務的實現和前端的交互可同時進行(註意這裏的接口集應該獨立在新建的程序集中而不是放在MVC應用程序集,後面基於IOC框架設計再擴展)
3.MVC應用程序使用的所有服務都托管在Ninject而不是散落在controller(甚至到頁面上), 對於安全策略,日誌記錄,錯誤處理可以集中處理,相當於對前端有了一個總閥
4.對於後端的擴展和模塊化設計提供了便捷,這點比較寬泛
附言:
MVC5中的NinjectWebCommon類的CreateKernel方法中提供了IHttpModule的Bind,這裏為喜歡玩管道的打開了一扇窗,讓這版MVC成了一個新的過渡
2.Activitor激活實現
這裏也是在ControllerBuilder初始化時做文章
public class NinjectControllerActivator : IControllerActivator { public IKernel Kernel { get; private set; } public NinjectControllerActivator() { this.Kernel = new StandardKernel(); AddBindings(); } public IController Create(RequestContext requestContext, Type controllerType) { return (IController)this.Kernel.TryGet(controllerType) as IController; } private void AddBindings() { this.Kernel.Bind<IEmployeeRepository>().To<EmployeeRepository>(); } }
對應在Global的Application_Start方法中是這樣告訴Builder的,這裏通過初始化CountrollerFactory對象實現服務註冊信息的註入
NinjectControllerActivator controllerActivator = new NinjectControllerActivator(); DefaultControllerFactory controllerFactory = new DefaultControllerFactory(controllerActivator); ControllerBuilder.Current.SetControllerFactory(controllerFactory);
看到ControllerFactory可能有人會想起Unity的方式,後面將Ninject比對下Unity
參考文章:
http://www.cnblogs.com/artech/archive/2012/04/01/controller-activation-032.html
http://www.cnblogs.com/stoneniqiu/p/4594642.html
IOC Of Ninject Base On ASP.NET MVC