动手造轮子：实现一个简单的依赖注入(二) --- 服务注册优化

Intro

之前实现的那版依赖注入框架基本可用，但是感觉还是不够灵活，而且注册服务和解析服务在同一个地方感觉有点别扭，有点职责分离不够。于是借鉴 Autofac 的做法，增加了一个 ServiceContainerBuilder 来负责注册服务，ServiceContainer负责解析服务，并且增加了一个 ServiceContainerModule 可以支持像 Autofac 中 Module/RegisterAssemblyModules 一样注册服务

实现代码

ServiceContainerBuilder

增加 ServiceContainerBuild 来专门负责注册服务，原来注册服务的那些扩展方法则从 IServiceContainer 的扩展方法变成 IServiceContainerBuilder 的扩展

public interface IServiceContainerBuilder{    IServiceContainerBuilder Add(ServiceDefinition item);    IServiceContainerBuilder TryAdd(ServiceDefinition item);    IServiceContainer Build();}public class ServiceContainerBuilder : IServiceContainerBuilder{    private readonly List
   
     _services = new List
    
     ();    public IServiceContainerBuilder Add(ServiceDefinition item)    {        if (_services.Any(_ => _.ServiceType == item.ServiceType && _.GetImplementType() == item.GetImplementType()))        {            return this;        }        _services.Add(item);        return this;    }    public IServiceContainerBuilder TryAdd(ServiceDefinition item)    {        if (_services.Any(_ => _.ServiceType == item.ServiceType))        {            return this;        }        _services.Add(item);        return this;    }    public IServiceContainer Build() => new ServiceContainer(_services);}

IServiceContainer

增加 ServiceContainerBuilder 之后就不再支持注册服务了，ServiceContainer 这个类型也可以变成一个内部类了，不必再对外暴露

public interface IServiceContainer : IScope, IServiceProvider{    IServiceContainer CreateScope();}internal class ServiceContainer : IServiceContainer{    private readonly IReadOnlyList
   
     _services;        public ServiceContainer(IReadOnlyList
    
      serviceDefinitions)    {        _services = serviceDefinitions;        // ...    }        // 此处约省略一万行代码 ...}

ServiceContainerModule

定义了一个 ServiceContainerModule 来实现像 Autofac 那样，在某一个程序集内定义一个 Module 注册程序集内需要注册的服务，在服务注册的地方调用 RegisterAssemblyModules 来扫描所有程序集并注册自定义 ServiceContainerModule 需要注册的服务

public interface IServiceContainerModule{    void ConfigureServices(IServiceContainerBuilder serviceContainerBuilder);}public abstract class ServiceContainerModule : IServiceContainerModule{    public abstract void ConfigureServices(IServiceContainerBuilder serviceContainerBuilder);}

自定义 ServiceContainerModule 使用示例：

public class TestServiceContainerModule : ServiceContainerModule{    public override void ConfigureServices(IServiceContainerBuilder serviceContainerBuilder)    {        serviceContainerBuilder.AddSingleton
   
    (GuidIdGenerator.Instance);    }}

RegisterAssemblyModules 扩展方法实现如下：

public static IServiceContainerBuilder RegisterAssemblyModules(    [NotNull] this IServiceContainerBuilder serviceContainerBuilder, params Assembly[] assemblies){    #if NET45        // 解决 asp.net 在 IIS 下应用程序域被回收的问题        // https://autofac.readthedocs.io/en/latest/register/scanning.html#iis-hosted-web-applications        if (null == assemblies || assemblies.Length == 0)        {            if (System.Web.Hosting.HostingEnvironment.IsHosted)            {                assemblies = System.Web.Compilation.BuildManager.GetReferencedAssemblies()                    .Cast
   
    ().ToArray();            }        }    #endif        if (null == assemblies || assemblies.Length == 0)        {            assemblies = AppDomain.CurrentDomain.GetAssemblies();        }    foreach (var type in assemblies.WhereNotNull().SelectMany(ass => ass.GetTypes())             .Where(t => t.IsClass && !t.IsAbstract && typeof(IServiceContainerModule).IsAssignableFrom(t))            )    {        try        {            if (Activator.CreateInstance(type) is ServiceContainerModule module)            {                module.ConfigureServices(serviceContainerBuilder);            }        }        catch (Exception e)        {            Console.WriteLine(e);        }    }    return serviceContainerBuilder;}

使用示例

使用起来除了注册服务变化了之外，别的地方并没有什么不同，看一下单元测试代码

public class DependencyInjectionTest : IDisposable{    private readonly IServiceContainer _container;    public DependencyInjectionTest()    {        var containerBuilder = new ServiceContainerBuilder();        containerBuilder.AddSingleton
   
    (new ConfigurationBuilder().Build());        containerBuilder.AddScoped
    
     ();        containerBuilder.AddScoped
     
      ();        containerBuilder.AddScoped
      
       ();        containerBuilder.AddScoped
       
        ();        containerBuilder.AddScoped
        
         (); containerBuilder.AddScoped
         
          (); containerBuilder.AddScoped(typeof(HasDependencyTest4<>)); containerBuilder.AddTransient
          
           (); containerBuilder.AddScoped
           
            (serviceProvider => new WuJing()); containerBuilder.AddSingleton(typeof(GenericServiceTest<>)); containerBuilder.RegisterAssemblyModules(); _container = containerBuilder.Build(); } [Fact] public void Test() { var rootConfig = _container.ResolveService
            
             (); Assert.Throws
             
              (() => _container.ResolveService
              
               ()); Assert.Throws
               
                (() => _container.ResolveRequiredService
                
                 ()); using (var scope = _container.CreateScope()) { var config = scope.ResolveService
                 
                  (); Assert.Equal(rootConfig, config); var fly1 = scope.ResolveRequiredService
                  
                   (); var fly2 = scope.ResolveRequiredService
                   
                    (); Assert.Equal(fly1, fly2); var wukong1 = scope.ResolveRequiredService
                    
                     (); var wukong2 = scope.ResolveRequiredService
                     
                      (); Assert.NotEqual(wukong1, wukong2); var wuJing1 = scope.ResolveRequiredService
                      
                       (); var wuJing2 = scope.ResolveRequiredService
                       
                        (); Assert.Equal(wuJing1, wuJing2); var s0 = scope.ResolveRequiredService
                        
                         (); s0.Test(); Assert.Equal(s0._fly, fly1); var s1 = scope.ResolveRequiredService
                         
                          (); s1.Test(); var s2 = scope.ResolveRequiredService
                          
                           (); s2.Test(); var s3 = scope.ResolveRequiredService
                           
                            (); s3.Test(); var s4 = scope.ResolveRequiredService
                            
                             
                              >(); s4.Test(); using (var innerScope = scope.CreateScope()) { var config2 = innerScope.ResolveRequiredService
                              
                               (); Assert.True(rootConfig == config2); var fly3 = innerScope.ResolveRequiredService
                               
                                (); fly3.Fly(); Assert.NotEqual(fly1, fly3); } var flySvcs = scope.ResolveServices
                                
                                 (); foreach (var f in flySvcs) f.Fly(); } var genericService1 = _container.ResolveRequiredService
                                 
                                  
                                   >(); genericService1.Test(); var genericService2 = _container.ResolveRequiredService
                                   
                                    
                                     >(); genericService2.Test(); } public void Dispose() { _container.Dispose(); }}

Reference

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