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最近在忙于 Fireasy 的重构,3.x 抛弃了 .Net Framework 时代的一些思想和模式,紧密拥抱 .Net Core,但它的思想仍然是开放性和灵活性。今天我主要来说说依赖注入与服务发现。
.Net Core 有自己的一套依赖注入,它的容器暴露给 IServiceCollection,通过在里面放入一些单例(Singleton)、瞬时(Transient)、作用域(Scoped)的一些服务描述(服务与实现的关系映射),这一部分我就不再细说了。
当然,一般常用的方式是,通过 AddSingleton、AddTransient 和 AddScoped 方法往容器里面加,但如果是依赖比较多的情况下(比如业务服务类),那你可能会经常忘了写这一部分代码了,而且也很难于维护。如常见的方式:
void ConfigureServices(IServiceCollection services) { services.AddTransient<IDeptmentService, DeptmentService>(); services.AddTransient<IRoleService, RoleService>(); services.AddTransient<IUserService, UserService>(); services.AddTransient<IDataRoleService, DataRoleService>(); //....... services.AddTransient<IProcessService, ProcessService>(); services.AddTransient<IWorkService, WorkService>(); }
有没有更简便更容易维护的方式呢?答案是当然有!
在 Fireasy,我们定义了三个服务接口,分别是 ISingletonService、ITransientService 和 IScopedService,这三个类只是一个标识,没有具体的方法和属性。使用需要注入的类实现此接口,如下:
public class DeptmentService : IDeptmentService, ITransientService { // ...... } public class DataRoleHelper : IDataRoleHelper, ISingletonService { // ...... }
好了,你只需在 ConfigureServices 里添加上这么一行代码,就能实现依赖注入:
void ConfigureServices(IServiceCollection services) { services.AddFireasy(); }
现在开始步入正题了,来看看 AddFireasy 是如何工作的。
IServiceDiscoverer 是用于服务发现的接口,它的默认实现是 DefaultServiceDiscoverer。如下:
public static SetupBuilder AddFireasy(this IServiceCollection services, Action<SetupOptions>? configure = null) { var options = new SetupOptions(); configure?.Invoke(options); var builder = new SetupBuilder(services, options); var discoverer = options.DiscoverOptions.DiscovererFactory == null ? new DefaultServiceDiscoverer(services, options.DiscoverOptions) : options.DiscoverOptions.DiscovererFactory(services, options.DiscoverOptions); if (discoverer != null) { services.AddSingleton<IServiceDiscoverer>(discoverer); } return builder; }
入口方法是 DiscoverServices,它会遍列程序目录下的所有程序集文件(*.dll),这里有程序集过滤器,你可以自己定义过滤规则。如下:
/// <summary> /// 发现工作目录中所有程序集中的依赖类型。 /// </summary> /// <param name="services"></param> private void DiscoverServices(IServiceCollection services) { foreach (var assembly in GetAssemblies()) { if (_options?.AssemblyFilters?.Any(s => s.IsFilter(assembly)) == true) { continue; } if (_options?.AssemblyFilterPredicates?.Any(s => s(assembly)) == true) { continue; } _assemblies.Add(assembly); ConfigureServices(services, assembly); DiscoverServices(services, assembly); } }
方法 DiscoverServices 用于对单个程序集进行服务发现并进行注册,这里同样也有类型过滤器,如下:
/// <summary> /// 发现程序集中的所有依赖类型。 /// </summary> /// <param name="services"></param> /// <param name="assembly"></param> private void DiscoverServices(IServiceCollection services, Assembly assembly) { foreach (var type in assembly.GetExportedTypes()) { if (_options?.TypeFilters?.Any(s => s.IsFilter(assembly, type)) == true) { continue; } if (_options?.TypeFilterPredicates?.Any(s => s(assembly, type)) == true) { continue; } ServiceLifetime? lifetime; var interfaceTypes = type.GetDirectImplementInterfaces().ToArray(); //如果使用标注 if (type.IsDefined(typeof(ServiceRegisterAttribute))) { lifetime = type.GetCustomAttribute<ServiceRegisterAttribute>()!.Lifetime; } else { lifetime = GetLifetimeFromType(type); } if (lifetime == null) { continue; } if (interfaceTypes.Length > 0) { interfaceTypes.ForEach(s => AddService(services, s, type, (ServiceLifetime)lifetime)); } else { AddService(services, type, type, (ServiceLifetime)lifetime); } } } private ServiceLifetime? GetLifetimeFromType(Type type) { if (typeof(ISingletonService).IsAssignableFrom(type)) { return ServiceLifetime.Singleton; } else if (typeof(ITransientService).IsAssignableFrom(type)) { return ServiceLifetime.Transient; } else if (typeof(IScopedService).IsAssignableFrom(type)) { return ServiceLifetime.Scoped; } return null; } private ServiceDescriptor AddService(IServiceCollection services, Type serviceType, Type implType, ServiceLifetime lifetime) { var descriptor = ServiceDescriptor.Describe(serviceType, implType, lifetime); _descriptors.Add(descriptor); services.Add(descriptor); return descriptor; }
从上面的代码中可看出,通过在程序集内部查找实现了 ISingletonService、ITransientService 或 IScopedService 的类,并将它们添加到 services 中,这样就完成了开篇提到的工作。
这里还出现了一个 ServiceRegisterAttribute,它在不实现以上三个接口的情况下,通过标注 Lifetime 生命周期来进行注册,一样达到了目的。
接下来做几个简单的单元测试。
单例测试:
/// <summary> /// 测试单例服务 /// </summary> [TestMethod] public void TestSingletonService() { var services = new ServiceCollection(); var builder = services.AddFireasy(); var serviceProvider = services.BuildServiceProvider(); var service1 = serviceProvider.GetService<ITestSingletonService>(); var service2 = serviceProvider.GetService<ITestSingletonService>(); Assert.IsNotNull(service1); Assert.IsNotNull(service2); //两对象的id应相等 Assert.AreEqual(service1.Id, service2.Id); } public interface ITestSingletonService { Guid Id { get; } void Test(); } public class TestSingletonServiceImpl : ITestSingletonService, ISingletonService { public TestSingletonServiceImpl() { Id = Guid.NewGuid(); } public Guid Id { get; } public void Test() => Console.WriteLine("Hello TestSingletonService!"); }
瞬时测试:
/// <summary> /// 测试瞬时服务 /// </summary> [TestMethod] public void TestTransientService() { var services = new ServiceCollection(); var builder = services.AddFireasy(); var serviceProvider = services.BuildServiceProvider(); var service1 = serviceProvider.GetService<ITestTransientService>(); var service2 = serviceProvider.GetService<ITestTransientService>(); Assert.IsNotNull(service1); Assert.IsNotNull(service2); //两对象的id应不相等 Assert.AreNotEqual(service1.Id, service2.Id); } public interface ITestTransientService { Guid Id { get; } void Test(); } public class TestTransientServiceImpl : ITestTransientService, ITransientService { public TestTransientServiceImpl() { Id = Guid.NewGuid(); } public Guid Id { get; } public void Test() => Console.WriteLine("Hello TestTransientService!"); }
作用域测试:
/// <summary> /// 测试作用域服务 /// </summary> [TestMethod] public void TestScopedService() { var services = new ServiceCollection(); var builder = services.AddFireasy(); var serviceProvider = services.BuildServiceProvider(); Guid id1, id2; //作用域1 using (var scope1 = serviceProvider.CreateScope()) { var service1 = scope1.ServiceProvider.GetService<ITestScopedService>(); var service2 = scope1.ServiceProvider.GetService<ITestScopedService>(); Assert.IsNotNull(service1); Assert.IsNotNull(service2); //两对象的id应相等 Assert.AreEqual(service1.Id, service2.Id); id1 = service1.Id; } //作用域2 using (var scope2 = serviceProvider.CreateScope()) { var service1 = scope2.ServiceProvider.GetService<ITestScopedService>(); var service2 = scope2.ServiceProvider.GetService<ITestScopedService>(); Assert.IsNotNull(service1); Assert.IsNotNull(service2); //两对象的id应相等 Assert.AreEqual(service1.Id, service2.Id); id2 = service1.Id; } //两次scoped的id应不相等 Assert.AreNotEqual(id1, id2); } public interface ITestScopedService { Guid Id { get; } void Test(); } public class TestScopedServiceImpl : ITestScopedService, IScopedService { public TestScopedServiceImpl() { Id = Guid.NewGuid(); } public Guid Id { get; } public void Test() => Console.WriteLine("Hello TestScopedService!"); }
可见,不需要显式 Add 也能将大量的服务类注入到容器中,不仅节省了大量的时间和代码,更是提高了程序的可维护性。
最后,奉上 Fireasy 3 的开源地址:https://gitee.com/faib920/fireasy3 ,欢迎大家前来捧场。
本文相关代码请参考 https://gitee.com/faib920/fireasy3/src/libraries/Fireasy.Common/DependencyInjection 下的相关文件。
更多内容请移步官网 http://www.fireasy.cn 。