private ILoginService<ApplicationUser> _loginService; public AccountController() { _loginService = new EFLoginService() }
public AccountController(ILoginService<ApplicationUser> loginService) { _loginService = loginService; }
把依赖的创建丢给其它人,自己只负责使用,其它人丢给你依赖的这个过程理解为注入。
public AccountController(ILoginService<ApplicationUser> loginService) { _loginService = loginService; }
javascript">// 用Redis来替换原来的EF登录 var controller = new AccountController(new RedisLoginService()); controller.Login(userName, password);
var serviceCollection = new ServiceCollection() .AddTransient<ILoginService, EFLoginService>() .AddSingleton<ILoginService, EFLoginService>() .AddScoped<ILoginService, EFLoginService>();
public interface IServiceCollection : IList<ServiceDescriptor> { }
我们上面的AddTransient、AddSignletone和Scoped方法是IServiceCollection的扩展方法, 都是往这个List里面添加ServiceDescriptor。
private static IServiceCollection Add( IServiceCollection collection, Type serviceType, Type implementationType, ServiceLifetime lifetime) { var descriptor = new ServiceDescriptor(serviceType, implementationType, lifetime); collection.Add(descriptor); return collection; }
public enum ServiceLifetime { Singleton, Scoped, Transient }
public interface IOperation { Guid OperationId { get; } } public interface IOperationSingleton : IOperation { } public interface IOperationTransient : IOperation{} public interface IOperationScoped : IOperation{}
我们的 Operation实现很简单,可以在构造函数中传入一个Guid进行赋值,如果没有的话则自已New一个 Guid。
public class Operation : IOperationSingleton, IOperationTransient, IOperationScoped { private Guid _guid; public Operation() { _guid = Guid.NewGuid(); } public Operation(Guid guid) { _guid = guid; } public Guid OperationId => _guid; }
在程序内我们可以多次调用ServiceProvider的GetService方法,获取到的都是同一个实例。
var services = new ServiceCollection(); // 默认构造 services.AddSingleton<IOperationSingleton, Operation>(); // 自定义传入Guid空值 services.AddSingleton<IOperationSingleton>( new Operation(Guid.Empty)); // 自定义传入一个New的Guid services.AddSingleton <IOperationSingleton>( new Operation(Guid.NewGuid())); var provider = services.BuildServiceProvider(); // 输出singletone1的Guid var singletone1 = provider.GetService<IOperationSingleton>(); Console.WriteLine($"signletone1: {singletone1.OperationId}"); // 输出singletone2的Guid var singletone2 = provider.GetService<IOperationSingleton>(); Console.WriteLine($"signletone2: {singletone2.OperationId}"); Console.WriteLine($"singletone1 == singletone2 ? : { singletone1 == singletone2 }");
我们对IOperationSingleton注册了三次,最后获取两次,大家要注意到我们获取到的始终都是我们最后一次注册的那个给了一个Guid的实例,前面的会被覆盖。
这次我们获取到的IOperationTransient为两个不同的实例。
var services = new ServiceCollection() .AddScoped<IOperationScoped, Operation>() .AddTransient<IOperationTransient, Operation>() .AddSingleton<IOperationSingleton, Operation>();
接下来我们用ServiceProvider.CreateScope方法创建一个Scope
var provider = services.BuildServiceProvider(); using (var scope1 = provider.CreateScope()) { var p = scope1.ServiceProvider; var scopeobj1 = p.GetService<IOperationScoped>(); var transient1 = p.GetService<IOperationTransient>(); var singleton1 = p.GetService<IOperationSingleton>(); var scopeobj2 = p.GetService<IOperationScoped>(); var transient2 = p.GetService<IOperationTransient>(); var singleton2 = p.GetService<IOperationSingleton>(); Console.WriteLine( $"scope1: { scopeobj1.OperationId }," + $"transient1: {transient1.OperationId}, " + $"singleton1: {singleton1.OperationId}"); Console.WriteLine($"scope2: { scopeobj2.OperationId }, " + $"transient2: {transient2.OperationId}, " + $"singleton2: {singleton2.OperationId}"); }
接下来
scope1: 200d1e63-d024-4cd3-88c9-35fdf5c00956,
transient1: fb35f570-713e-43fc-854c-972eed2fae52,
singleton1: da6cf60f-670a-4a86-8fd6-01b635f74225
scope2: 200d1e63-d024-4cd3-88c9-35fdf5c00956,
transient2: 2766a1ee-766f-4116-8a48-3e569de54259,
singleton2: da6cf60f-670a-4a86-8fd6-01b635f74225
如果再创建一个新的Scope运行,
scope1: 29f127a7-baf5-4ab0-b264-fcced11d0729,
transient1: 035d8bfc-c516-44a7-94a5-3720bd39ce57,
singleton1: da6cf60f-670a-4a86-8fd6-01b635f74225
scope2: 29f127a7-baf5-4ab0-b264-fcced11d0729,
transient2: 74c37151-6497-4223-b558-a4ffc1897d57,
singleton2: da6cf60f-670a-4a86-8fd6-01b635f74225
大家注意到上面我们一共得到了 4个Transient实例,2个Scope实例,1个Singleton实例。
public void ConfigureServices(IServiceCollection services) { services.AddTransient<ILoginService<ApplicationUser>, EFLoginService>(); services.AddMvc(); )
ASP.NET Core的一些组件已经提供了一些实例的绑定,像AddMvc就是Mvc Middleware在 IServiceCollection上添加的扩展方法。
public static IMvcBuilder AddMvc(this IServiceCollection services) { if (services == null) { throw new ArgumentNullException(nameof(services)); } var builder = services.AddMvcCore(); builder.AddApiExplorer(); builder.AddAuthorization(); AddDefaultFrameworkParts(builder.PartManager); ... }
private ILoginService<ApplicationUser> _loginService; public AccountController( ILoginService<ApplicationUser> loginService) { _loginService = loginService; }
我们只要在控制器的构造函数里面写了这个参数,ServiceProvider就会帮我们注入进来。这一步是在Mvc初始化控制器的时候完成的,我们后面再介绍到Mvc的时候会往细里讲。
@using MilkStone.Services; @model MilkStone.Models.AccountViewModel.LoginViewModel @inject ILoginService<ApplicationUser> loginService <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head></head> <body> @loginService.GetUserName() </body> </html>
HttpContext.RequestServices.GetService<ILoginService<ApplicationUser>>();
builder.RegisterGeneric(typeof(LoggingBehavior<,>)).As(typeof(IPipelineBehavior<,>)); builder.RegisterGeneric(typeof(ValidatorBehavior<,>)).As(typeof(IPipelineBehavior<,>));
这会给我们的初始化带来一些便利性,我们来看看如何替换Autofac到ASP.NET Core。我们只需要把Startup类里面的 ConfigureService的 返回值从 void改为 IServiceProvider即可。而返回的则是一个AutoServiceProvider。
public IServiceProvider ConfigureServices( IServiceCollection services){ services.AddMvc(); // Add other framework services // Add Autofac var containerBuilder = new ContainerBuilder(); containerBuilder.RegisterModule<DefaultModule>(); containerBuilder.Populate(services); var container = containerBuilder.Build(); return new AutofacServiceProvider(container); }