net core天马行空系列： 一个接口多个实现类，利用mixin技术通过自定义服务名，实现精准属性注入
系列目录
1.net core天马行空系列：原生DI+AOP实现spring boot注解式编程
2.net core天马行空系列： 泛型仓储和声明式事物实现最优雅的crud操作
哈哈哈哈，大家好，我就是高产似母猪的三合。日常开发中，我们常会遇到这样的场景，一个接口，有多个实现类，在某个业务中，我们希望指定某个实现类，如今网络上常见的解决方案，就是注入一个委托或者利用工厂模式，这些方式虽然能实现功能，但使用起来还是不够优雅，如何才称得上优雅呢？自然是在添加服务的时候给服务指定名称，注入的时候根据名称来进行注入，没错，就是类似spring boot里的@Qualifier注解，那么net core能实现这个注解么？要知道net core里的原生DI并不支持在注册的时候给服务添加名称，所以实现起来也是难上加难，但是，利用动态代理，我们就能完美解决这个问题，没错，他Lei了，net core版[QualifierAttribute],实现这个注解用到的最核心的技术，就是动态代理中非常重要的mixin，什么是mixin呢？玩过less的小伙伴可能会知道，这玩意可以把2个css样式混合成一个，而在net core中，DP(castle.dynamicproxy)提供的mixin技术，可以在程序运行时，把多个类混合成一个动态代理类，这个混合类既可以用作类1，又可以用作类2，那么思路就很清晰了，类1就是我们注入的服务类，类2需要我们自定义，在我们的这个自定义类中，我们可以添加一个Name的属性，这样在注册服务的时候给服务命名，到了注入的时候，我们就可以根据名称来进行精准地的属性注入。BTW,动态代理，注解式编程，AOP贯穿本系列始终，no bb，正文开始。
1.定义用到的类
定义QualifierAttribute注解
public class QualifierAttribute : Attribute { public string Name { get; } public QualifierAttribute(string name) { if (string.IsNullOrWhiteSpace(name)) { throw new ArgumentException("服务名称不能为空"); } this.Name = name; } }
定义用来进行混合的附加类接口IDependencyAddition和他的实现类DependencyAddition，类里面只有一个名称的属性。
public interface IDependencyAddition { string Name { set; get; } }
public class DependencyAddition : IDependencyAddition { public string Name { set; get; } }
第一篇文章里，讲过有一辆汽车，汽车里有引擎，我们在这基础上进行扩展，汽车总是有轮胎的，我们定义一个轮胎接口IWheel和他的2个实现类WheelA和WheelB，类里只有一个Scroll方法，表示轮胎在滚，同时向控制台输出他们是哪种轮胎。
public interface IWheel { void Scroll(); }
public class WheelA : IWheel { public void Scroll() { Console.WriteLine("我是A轮胎，我正在滚"); } }
public class WheelB : IWheel { public void Scroll() { Console.WriteLine("我是B轮胎，我正在滚"); } }
修改汽车类接口ICar和他的实现类Car，主要就是添加了轮胎的属性注入，并且用[Qualifier("B轮胎")]注解指定使用哪种轮胎，然后调用Scroll方法，让轮胎滚起来。
public interface ICar { Engine Engine { set; get; } IWheel Wheel { set; get; } void Fire(); }
public class Car : ICar { [Autowired] public Engine Engine { set; get; } [Value("oilNo")] public int OilNo { set; get; } [Autowired] [Qualifier("B轮胎")] public IWheel Wheel { set; get; } [Transactional] public void Fire() { Console.WriteLine("加满" + OilNo + "号汽油,点火"); Wheel.Scroll(); Engine.Start(); } }
IServiceCollection的静态扩展类SummerBootExtentions，和上一篇相比，主要是添加了AddSbService的新重载，使注册服务的时候能够为服务添加名称，在这基础上进一步封装了AddSbSingleton，AddSbScoped和AddSbTransient方法。还有在工厂委托函数里进行属性注入的时候，添加了支持[QualifierAttribute]注解的逻辑，完整类代码如下：
public static class SummerBootExtentions { /// <summary> /// 瞬时 /// </summary> /// <typeparam name="TService"></typeparam> /// <typeparam name="TImplementation"></typeparam> /// <param name="services"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbTransient<TService, TImplementation>(this IServiceCollection services, params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), typeof(TImplementation), ServiceLifetime.Transient, interceptorTypes); } /// <summary> /// 瞬时 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="implementationType"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbTransient(this IServiceCollection services, Type serviceType, Type implementationType, params Type[] interceptorTypes) { return services.AddSbService(serviceType, implementationType, ServiceLifetime.Transient, interceptorTypes); } /// <summary> /// 请求级别 /// </summary> /// <typeparam name="TService"></typeparam> /// <typeparam name="TImplementation"></typeparam> /// <param name="services"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbScoped<TService, TImplementation>(this IServiceCollection services, params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), typeof(TImplementation), ServiceLifetime.Scoped, interceptorTypes); } /// <summary> /// 请求级别 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="implementationType"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbScoped(this IServiceCollection services, Type serviceType, Type implementationType, params Type[] interceptorTypes) { return services.AddSbService(serviceType, implementationType, ServiceLifetime.Scoped, interceptorTypes); } /// <summary> /// 单例 /// </summary> /// <typeparam name="TService"></typeparam> /// <typeparam name="TImplementation"></typeparam> /// <param name="services"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbSingleton<TService, TImplementation>(this IServiceCollection services, params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), typeof(TImplementation), ServiceLifetime.Singleton, interceptorTypes); } /// <summary> /// 单例 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="implementationType"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbSingleton(this IServiceCollection services, Type serviceType, Type implementationType, params Type[] interceptorTypes) { return services.AddSbService(serviceType, implementationType, ServiceLifetime.Singleton, interceptorTypes); } public static IServiceCollection AddSbService(this IServiceCollection services, Type serviceType, Type implementationType, ServiceLifetime lifetime, params Type[] interceptorTypes) { services.Add(new ServiceDescriptor(implementationType, implementationType, lifetime)); object Factory(IServiceProvider provider) { var target = provider.GetService(implementationType); var properties = implementationType.GetTypeInfo().DeclaredProperties; foreach (PropertyInfo info in properties) { //属性注入 if (info.GetCustomAttribute<AutowiredAttribute>() != null) { var propertyType = info.PropertyType; object impl = null; var qualifierAttribute = info.GetCustomAttribute<QualifierAttribute>(); if (qualifierAttribute != null) { var serviceName = qualifierAttribute.Name; var implList = provider.GetServices(propertyType); foreach (var tmpImpl in implList) { if (ProxyUtil.IsProxy(tmpImpl)) { var addition = tmpImpl as IDependencyAddition; if (addition?.Name == serviceName) { impl = tmpImpl; break; ; } } } } else { impl = provider.GetService(propertyType); } if (impl != null) { info.SetValue(target, impl); } } //配置值注入 if (info.GetCustomAttribute<ValueAttribute>() is ValueAttribute valueAttribute) { var value = valueAttribute.Value; if (provider.GetService(typeof(IConfiguration)) is IConfiguration configService) { var pathValue = configService.GetSection(value).Value; if (pathValue != null) { var pathV = Convert.ChangeType(pathValue, info.PropertyType); info.SetValue(target, pathV); } } } } List<IInterceptor> interceptors = interceptorTypes.ToList() .ConvertAll<IInterceptor>(interceptorType => provider.GetService(interceptorType) as IInterceptor); var proxyGenerator = provider.GetService<ProxyGenerator>(); var proxy = proxyGenerator.CreateInterfaceProxyWithTarget(serviceType, target, interceptors.ToArray()); return proxy; }; var serviceDescriptor = new ServiceDescriptor(serviceType, Factory, lifetime); services.Add(serviceDescriptor); return services; } /// <summary> /// 瞬时 /// </summary> /// <typeparam name="TService"></typeparam> /// <param name="services"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbTransient<TService>(this IServiceCollection services, params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), ServiceLifetime.Transient, interceptorTypes); } /// <summary> /// 瞬时 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbTransient(this IServiceCollection services, Type serviceType, params Type[] interceptorTypes) { return services.AddSbService(serviceType, ServiceLifetime.Transient, interceptorTypes); } /// <summary> /// 请求 /// </summary> /// <typeparam name="TService"></typeparam> /// <param name="services"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbScoped<TService>(this IServiceCollection services, params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), ServiceLifetime.Scoped, interceptorTypes); } /// <summary> /// 请求 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbScoped(this IServiceCollection services, Type serviceType, params Type[] interceptorTypes) { return services.AddSbService(serviceType, ServiceLifetime.Scoped, interceptorTypes); } /// <summary> /// 单例 /// </summary> /// <typeparam name="TService"></typeparam> /// <param name="services"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbSingleton<TService>(this IServiceCollection services, params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), ServiceLifetime.Singleton, interceptorTypes); } /// <summary> /// 单例 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbSingleton(this IServiceCollection services, Type serviceType, params Type[] interceptorTypes) { return services.AddSbService(serviceType, ServiceLifetime.Singleton, interceptorTypes); } public static IServiceCollection AddSbService(this IServiceCollection services, Type serviceType, ServiceLifetime lifetime, params Type[] interceptorTypes) { if (services == null) throw new ArgumentNullException(nameof(services)); if (serviceType == (Type)null) throw new ArgumentNullException(nameof(serviceType)); object Factory(IServiceProvider provider) { List<IInterceptor> interceptors = interceptorTypes.ToList() .ConvertAll<IInterceptor>(interceptorType => provider.GetService(interceptorType) as IInterceptor); var proxyGenerator = provider.GetService<ProxyGenerator>(); var proxy = proxyGenerator.CreateClassProxy(serviceType, interceptors.ToArray()); var properties = serviceType.GetTypeInfo().DeclaredProperties; foreach (PropertyInfo info in properties) { //属性注入 if (info.GetCustomAttribute<AutowiredAttribute>() != null) { var propertyType = info.PropertyType; object impl = null; var qualifierAttribute = info.GetCustomAttribute<QualifierAttribute>(); if (qualifierAttribute != null) { var serviceName = qualifierAttribute.Name; var implList = provider.GetServices(propertyType); foreach (var tmpImpl in implList) { if (ProxyUtil.IsProxy(tmpImpl)) { var addition = tmpImpl as IDependencyAddition; if (addition?.Name == serviceName) { impl = tmpImpl; break; ; } } } } else { impl = provider.GetService(propertyType); } if (impl != null) { info.SetValue(proxy, impl); } } //配置值注入 if (info.GetCustomAttribute<ValueAttribute>() is ValueAttribute valueAttribute) { var value = valueAttribute.Value; if (provider.GetService(typeof(IConfiguration)) is IConfiguration configService) { var pathValue = configService.GetSection(value).Value; if (pathValue != null) { var pathV = Convert.ChangeType(pathValue, info.PropertyType); info.SetValue(proxy, pathV); } } } } return proxy; }; var serviceDescriptor = new ServiceDescriptor(serviceType, Factory, lifetime); services.Add(serviceDescriptor); return services; } /// <summary> /// 添加summer boot扩展 /// </summary> /// <param name="builder"></param> /// <returns></returns> public static IMvcBuilder AddSB(this IMvcBuilder builder) { if (builder == null) throw new ArgumentNullException(nameof(builder)); ControllerFeature feature = new ControllerFeature(); builder.PartManager.PopulateFeature<ControllerFeature>(feature); foreach (Type type in feature.Controllers.Select<TypeInfo, Type>((Func<TypeInfo, Type>)(c => c.AsType()))) builder.Services.TryAddTransient(type, type); builder.Services.Replace(ServiceDescriptor.Transient<IControllerActivator, SbControllerActivator>()); return builder; } public static IServiceCollection AddSbRepositoryService(this IServiceCollection services, params Type[] interceptorTypes) { var types = AppDomain.CurrentDomain.GetAssemblies().SelectMany(it => it.GetTypes()); var tableType = types.Where(it => it.GetCustomAttribute<TableAttribute>() != null); foreach (var type in tableType) { var injectServiceType = typeof(IRepository<>).MakeGenericType(type); var injectImplType = typeof(BaseRepository<>).MakeGenericType(type); services.AddSbScoped(injectServiceType, injectImplType, interceptorTypes); } return services; } /// <summary> /// 瞬时 /// </summary> /// <typeparam name="TService"></typeparam> /// <typeparam name="TImplementation"></typeparam> /// <param name="services"></param> /// <param name="name"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbTransient<TService, TImplementation>(this IServiceCollection services, string name = "", params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), typeof(TImplementation), ServiceLifetime.Transient, name, interceptorTypes); } /// <summary> /// 瞬时 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="implementationType"></param> /// <param name="name"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbTransient(this IServiceCollection services, Type serviceType, Type implementationType, string name = "", params Type[] interceptorTypes) { return services.AddSbService(serviceType, implementationType, ServiceLifetime.Transient, name, interceptorTypes); } /// <summary> /// 请求级别 /// </summary> /// <typeparam name="TService"></typeparam> /// <typeparam name="TImplementation"></typeparam> /// <param name="services"></param> /// <param name="name"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbScoped<TService, TImplementation>(this IServiceCollection services, string name = "", params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), typeof(TImplementation), ServiceLifetime.Scoped, name, interceptorTypes); } /// <summary> /// 请求级别 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="implementationType"></param> /// <param name="name"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbScoped(this IServiceCollection services, Type serviceType, Type implementationType, string name = "", params Type[] interceptorTypes) { return services.AddSbService(serviceType, implementationType, ServiceLifetime.Scoped, name, interceptorTypes); } /// <summary> /// 单例 /// </summary> /// <typeparam name="TService"></typeparam> /// <typeparam name="TImplementation"></typeparam> /// <param name="services"></param> /// <param name="name"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbSingleton<TService, TImplementation>(this IServiceCollection services, string name = "", params Type[] interceptorTypes) { return services.AddSbService(typeof(TService), typeof(TImplementation), ServiceLifetime.Singleton, name, interceptorTypes); } /// <summary> /// 单例 /// </summary> /// <param name="services"></param> /// <param name="serviceType"></param> /// <param name="implementationType"></param> /// <param name="name"></param> /// <param name="interceptorTypes"></param> /// <returns></returns> public static IServiceCollection AddSbSingleton(this IServiceCollection services, Type serviceType, Type implementationType, string name = "", params Type[] interceptorTypes) { return services.AddSbService(serviceType, implementationType, ServiceLifetime.Singleton, name, interceptorTypes); } public static IServiceCollection AddSbService(this IServiceCollection services, Type serviceType, Type implementationType, ServiceLifetime lifetime, string name = "", params Type[] interceptorTypes) { services.Add(new ServiceDescriptor(implementationType, implementationType, lifetime)); object Factory(IServiceProvider provider) { var target = provider.GetService(implementationType); var properties = implementationType.GetTypeInfo().DeclaredProperties; foreach (PropertyInfo info in properties) { //属性注入 if (info.GetCustomAttribute<AutowiredAttribute>() != null) { var propertyType = info.PropertyType; object impl = null; var qualifierAttribute = info.GetCustomAttribute<QualifierAttribute>(); if (qualifierAttribute != null) { var serviceName = qualifierAttribute.Name; var implList = provider.GetServices(propertyType); foreach (var tmpImpl in implList) { if (ProxyUtil.IsProxy(tmpImpl)) { var addition = tmpImpl as IDependencyAddition; if (addition?.Name == serviceName) { impl = tmpImpl; break; ; } } } } else { impl = provider.GetService(propertyType); } if (impl != null) { info.SetValue(target, impl); } } //配置值注入 if (info.GetCustomAttribute<ValueAttribute>() is ValueAttribute valueAttribute) { var value = valueAttribute.Value; if (provider.GetService(typeof(IConfiguration)) is IConfiguration configService) { var pathValue = configService.GetSection(value).Value; if (pathValue != null) { var pathV = Convert.ChangeType(pathValue, info.PropertyType); info.SetValue(target, pathV); } } } } List<IInterceptor> interceptors = interceptorTypes.ToList() .ConvertAll<IInterceptor>(interceptorType => provider.GetService(interceptorType) as IInterceptor); var proxyGenerator = provider.GetService<ProxyGenerator>(); var options = new ProxyGenerationOptions(); options.AddMixinInstance(new DependencyAddition() { Name = name }); var proxy = proxyGenerator.CreateInterfaceProxyWithTarget(serviceType, target, options, interceptors.ToArray()); return proxy; }; var serviceDescriptor = new ServiceDescriptor(serviceType, Factory, lifetime); services.Add(serviceDescriptor); return services; } }
修改第一篇中自定义的控制器激活类SbControllerActivator，添加支持[QualifierAttribute]注解的逻辑。
public class SbControllerActivator : IControllerActivator { /// <inheritdoc /> public object Create(ControllerContext actionContext) { if (actionContext == null) throw new ArgumentNullException(nameof(actionContext)); Type serviceType = actionContext.ActionDescriptor.ControllerTypeInfo.AsType(); var target = actionContext.HttpContext.RequestServices.GetRequiredService(serviceType); var properties = serviceType.GetTypeInfo().DeclaredProperties; var proxyGenerator = actionContext.HttpContext.RequestServices.GetService<ProxyGenerator>(); var proxy = proxyGenerator.CreateClassProxyWithTarget(serviceType, target); foreach (PropertyInfo info in properties) { //属性注入 if (info.GetCustomAttribute<AutowiredAttribute>() != null) { var propertyType = info.PropertyType; object impl = null; var qualifierAttribute = info.GetCustomAttribute<QualifierAttribute>(); if (qualifierAttribute != null) { var serviceName = qualifierAttribute.Name; var implList = actionContext.HttpContext.RequestServices.GetServices(propertyType); foreach (var tmpImpl in implList) { if (ProxyUtil.IsProxy(tmpImpl)) { var addition = tmpImpl as IDependencyAddition; if (addition?.Name == serviceName) { impl = tmpImpl; break; ; } } } } else { impl = actionContext.HttpContext.RequestServices.GetService(propertyType); } if (impl != null) { info.SetValue(proxy, impl); } } //配置值注入 if (info.GetCustomAttribute<ValueAttribute>() is ValueAttribute valueAttribute) { var value = valueAttribute.Value; if (actionContext.HttpContext.RequestServices.GetService(typeof(IConfiguration)) is IConfiguration configService) { var pathValue = configService.GetSection(value).Value; if (pathValue != null) { var pathV = Convert.ChangeType(pathValue, info.PropertyType); info.SetValue(proxy, pathV); } } } } return proxy; } /// <inheritdoc /> public virtual void Release(ControllerContext context, object controller) { } }
修改Startup.cs类里的ConfigureServices方法，可以看到，我们在注册WheelA和WheelB的时候，为服务添加了名称，并且随手添加了个拦截器，代码如下:
public void ConfigureServices(IServiceCollection services) { services.Configure<CookiePolicyOptions>(options => { // This lambda determines whether user consent for non-essential cookies is needed for a given request. options.CheckConsentNeeded = context => true; options.MinimumSameSitePolicy = SameSiteMode.None; }); services.AddMvc() .SetCompatibilityVersion(CompatibilityVersion.Version_2_1) .AddSB(); services.AddSingleton<ProxyGenerator>(); services.AddSbScoped<Engine>(typeof(TransactionalInterceptor)); services.AddSbScoped<IUnitOfWork, UnitOfWork>(); services.AddScoped(typeof(TransactionalInterceptor)); services.AddSbScoped<ICar, Car>(typeof(TransactionalInterceptor)); services.AddSbScoped<IDbFactory, DbFactory>(); services.AddSbRepositoryService(typeof(TransactionalInterceptor)); services.AddSbScoped<IAddOilService, AddOilService>(typeof(TransactionalInterceptor)); services.AddSbScoped<IWheel, WheelA>("A轮胎", typeof(TransactionalInterceptor)); services.AddSbScoped<IWheel, WheelB>("B轮胎", typeof(TransactionalInterceptor)); }
控制器类HomeController，代码如下：
public class HomeController : Controller { [Autowired] public ICar Car { set; get; } [Autowired] public IDistributedCache Cache { set; get; } [Value("description")] public string Description { set; get; } [Autowired] public IAddOilService AddOilService { set; get; } public IActionResult Index() { var car = Car; AddOilService.AddOil(); Car.Fire(); Console.WriteLine(Description); return View(); } }
核心原理，从SummerBootExtentions类完整源码里单独抽取mixin服务注册和属性注入的代码，可以看到在生成动态代理的时候，在option里添加了mixin实例，也就是我们自定义的DependencyAddition，里面包含了这个服务的名称，在注入时，判断是否有[QualifierAttribute]注解，如果有，就获取整个接口的实现类列表，在循环里，判断是否为动态代理类，如果是，就把每个类实例强转为附加类接口IDependencyAddition，然后获取名称，如果名称和我们[QualifierAttribute]注解指定的名称相同，则注入。
var proxyGenerator = provider.GetService<ProxyGenerator>(); var options = new ProxyGenerationOptions(); options.AddMixinInstance(new DependencyAddition() { Name = name }); var proxy = proxyGenerator.CreateInterfaceProxyWithTarget(serviceType, target, options, interceptors.ToArray());
//属性注入 if (info.GetCustomAttribute<AutowiredAttribute>() != null) { var propertyType = info.PropertyType; object impl = null; var qualifierAttribute = info.GetCustomAttribute<QualifierAttribute>(); if (qualifierAttribute != null) { var serviceName = qualifierAttribute.Name; var implList = provider.GetServices(propertyType); foreach (var tmpImpl in implList) { if (ProxyUtil.IsProxy(tmpImpl)) { var addition = tmpImpl as IDependencyAddition; if (addition?.Name == serviceName) { impl = tmpImpl; break; ; } } } } else { impl = provider.GetService(propertyType); } if (impl != null) { info.SetValue(target, impl); } }
2.效果图
先注入A轮胎
从上图可以看到，生成的动态代理类里包含了Name这个属性，并且名称为A轮胎。
控制台输出，也显示了“我是A轮胎，我正在滚”，符合预期。
注入B轮胎
从上图可以看到，生成的动态代理类里包含了Name这个属性，并且名称为B轮胎。
控制台输出，也显示了“我是B轮胎，我正在滚”，符合预期。
3. 写在最后
通过[Autowired]注解和[Qualifier("B轮胎")]注解联合使用，我们就实现了一个接口多个实现类的精准属性注入，代码看起来是不是舒服多了呢~，我始终相信，如果一件事我讲的别人听不明白，那一定是我讲的不够有趣，不够通俗易懂，所以大白话是必须的，如果文章还有哪里说得太深奥，欢迎给我指出来，同时net core里还有啥功能让你觉得用起来特别别扭的，请！一定！告诉我！，i will try it，因为这特别有趣，因为我一直践行的编程理念就是万物靠注入，万物可拦截，万物皆注解，始终相信IOC和AOP是构建软件的基石，哈哈哈哈哈。
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