動(dòng)手造輪子：實(shí)現(xiàn)一個(gè)簡(jiǎn)單的依賴(lài)注入(二) --- 服務(wù)注冊(cè)優(yōu)化

Intro

之前實(shí)現(xiàn)的那版依賴(lài)注入框架基本可用，但是感覺(jué)還是不夠靈活，而且注冊(cè)服務(wù)和解析服務(wù)在同一個(gè)地方感覺(jué)有點(diǎn)別扭，有點(diǎn)職責(zé)分離不夠。于是借鑒 Autofac 的做法，增加了一個(gè) ServiceContainerBuilder 來(lái)負(fù)責(zé)注冊(cè)服務(wù)，ServiceContainer負(fù)責(zé)解析服務(wù)，并且增加了一個(gè) ServiceContainerModule 可以支持像 Autofac 中 Module/RegisterAssemblyModules 一樣注冊(cè)服務(wù)

實(shí)現(xiàn)代碼

ServiceContainerBuilder

增加 ServiceContainerBuild 來(lái)專(zhuān)門(mén)負(fù)責(zé)注冊(cè)服務(wù)，原來(lái)注冊(cè)服務(wù)的那些擴(kuò)展方法則從 IServiceContainer 的擴(kuò)展方法變成 IServiceContainerBuilder 的擴(kuò)展

public interface IServiceContainerBuilder
{
    IServiceContainerBuilder Add(ServiceDefinition item);

    IServiceContainerBuilder TryAdd(ServiceDefinition item);

    IServiceContainer Build();
}

public class ServiceContainerBuilder : IServiceContainerBuilder
{
    private readonly List<ServiceDefinition> _services = new List<ServiceDefinition>();

    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 之后就不再支持注冊(cè)服務(wù)了，ServiceContainer 這個(gè)類(lèi)型也可以變成一個(gè)內(nèi)部類(lèi)了，不必再對(duì)外暴露

public interface IServiceContainer : IScope, IServiceProvider
{
    IServiceContainer CreateScope();
}

internal class ServiceContainer : IServiceContainer
{
    private readonly IReadOnlyList<ServiceDefinition> _services;
    
    public ServiceContainer(IReadOnlyList<ServiceDefinition> serviceDefinitions)
    {
        _services = serviceDefinitions;
        // ...
    }
    
    // 此處約省略一萬(wàn)行代碼 ...
}

ServiceContainerModule

定義了一個(gè) ServiceContainerModule 來(lái)實(shí)現(xiàn)像 Autofac 那樣，在某一個(gè)程序集內(nèi)定義一個(gè) Module 注冊(cè)程序集內(nèi)需要注冊(cè)的服務(wù)，在服務(wù)注冊(cè)的地方調(diào)用 RegisterAssemblyModules 來(lái)掃描所有程序集并注冊(cè)自定義 ServiceContainerModule 需要注冊(cè)的服務(wù)

public interface IServiceContainerModule
{
    void ConfigureServices(IServiceContainerBuilder serviceContainerBuilder);
}

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

自定義 ServiceContainerModule 使用示例：

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

RegisterAssemblyModules 擴(kuò)展方法實(shí)現(xiàn)如下：

public static IServiceContainerBuilder RegisterAssemblyModules(
    [NotNull] this IServiceContainerBuilder serviceContainerBuilder, params Assembly[] assemblies)
{
    #if NET45
        // 解決 asp.net 在 IIS 下應(yīng)用程序域被回收的問(wèn)題
        // 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<Assembly>().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

使用起來(lái)除了注冊(cè)服務(wù)變化了之外，別的地方并沒(méi)有什么不同，看一下單元測(cè)試代碼

public class DependencyInjectionTest : IDisposable
{
    private readonly IServiceContainer _container;

    public DependencyInjectionTest()
    {
        var containerBuilder = new ServiceContainerBuilder();
        containerBuilder.AddSingleton<IConfiguration>(new ConfigurationBuilder().Build());
        containerBuilder.AddScoped<IFly, MonkeyKing>();
        containerBuilder.AddScoped<IFly, Superman>();

        containerBuilder.AddScoped<HasDependencyTest>();
        containerBuilder.AddScoped<HasDependencyTest1>();
        containerBuilder.AddScoped<HasDependencyTest2>();
        containerBuilder.AddScoped<HasDependencyTest3>();
        containerBuilder.AddScoped(typeof(HasDependencyTest4<>));

        containerBuilder.AddTransient<WuKong>();
        containerBuilder.AddScoped<WuJing>(serviceProvider => new WuJing());
        containerBuilder.AddSingleton(typeof(GenericServiceTest<>));
        
        containerBuilder.RegisterAssemblyModules();

        _container = containerBuilder.Build();
    }

    [Fact]
    public void Test()
    {
        var rootConfig = _container.ResolveService<IConfiguration>();

        Assert.Throws<InvalidOperationException>(() => _container.ResolveService<IFly>());
        Assert.Throws<InvalidOperationException>(() => _container.ResolveRequiredService<IDependencyResolver>());

        using (var scope = _container.CreateScope())
        {
            var config = scope.ResolveService<IConfiguration>();

            Assert.Equal(rootConfig, config);

            var fly1 = scope.ResolveRequiredService<IFly>();
            var fly2 = scope.ResolveRequiredService<IFly>();
            Assert.Equal(fly1, fly2);

            var wukong1 = scope.ResolveRequiredService<WuKong>();
            var wukong2 = scope.ResolveRequiredService<WuKong>();

            Assert.NotEqual(wukong1, wukong2);

            var wuJing1 = scope.ResolveRequiredService<WuJing>();
            var wuJing2 = scope.ResolveRequiredService<WuJing>();

            Assert.Equal(wuJing1, wuJing2);

            var s0 = scope.ResolveRequiredService<HasDependencyTest>();
            s0.Test();
            Assert.Equal(s0._fly, fly1);

            var s1 = scope.ResolveRequiredService<HasDependencyTest1>();
            s1.Test();

            var s2 = scope.ResolveRequiredService<HasDependencyTest2>();
            s2.Test();

            var s3 = scope.ResolveRequiredService<HasDependencyTest3>();
            s3.Test();

            var s4 = scope.ResolveRequiredService<HasDependencyTest4<string>>();
            s4.Test();

            using (var innerScope = scope.CreateScope())
            {
                var config2 = innerScope.ResolveRequiredService<IConfiguration>();
                Assert.True(rootConfig == config2);

                var fly3 = innerScope.ResolveRequiredService<IFly>();
                fly3.Fly();

                Assert.NotEqual(fly1, fly3);
            }

            var flySvcs = scope.ResolveServices<IFly>();
            foreach (var f in flySvcs)
                f.Fly();
        }

        var genericService1 = _container.ResolveRequiredService<GenericServiceTest<int>>();
        genericService1.Test();

        var genericService2 = _container.ResolveRequiredService<GenericServiceTest<string>>();
        genericService2.Test();
    }

    public void Dispose()
    {
        _container.Dispose();
    }
}

Reference

• https://github.com/WeihanLi/WeihanLi.Common/tree/dev/src/WeihanLi.Common/DependencyInjection
• https://www.cnblogs.com/weihanli/p/implement-dependency-injection-01.html
• https://www.cnblogs.com/weihanli/p/implement-dependency-injection.html
• https://autofac.org/
• https://autofac.readthedocs.io/en/latest/register/scanning.html