Hand made wheel: to realize a simple dependency injection (2) -- service registration optimization

Intro

The previous version of dependency injection framework is basically available, but it still feels inflexible, and the registration service and resolution service are a bit awkward in the same place, and the separation of responsibilities is not enough. Therefore, a ServiceContainerBuilder is added to register services, a ServiceContainer is added to resolve services, and a ServiceContainerModule is added to support registering services like Module/RegisterAssemblyModules in Autofac

Implementation code

ServiceContainerBuilder

Add ServiceContainerBuild to be responsible for registering services. The extension methods of the original registered services are changed from the extension methods of IServiceContainer to the extension methods of IServiceContainerBuilder

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

After adding ServiceContainerBuilder, it will no longer support registering services. The ServiceContainer type can also become an internal class, so it does not need to be exposed to the outside world

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

internal class ServiceContainer : IServiceContainer
{
    private readonly IReadOnlyList<ServiceDefinition> _services;
    
    public ServiceContainer(IReadOnlyList<ServiceDefinition> serviceDefinitions)
    {
        _services = serviceDefinitions;
        // ...
    }
    
    // About 10000 lines of code are omitted here
}

ServiceContainerModule

A ServiceContainerModule is defined to implement services that need to be registered in a Module registration assembly in an assembly like Autofac. RegisterAssemblyModules is called in the service registration place to scan all assemblies and register services that need to be registered in the custom ServiceContainerModule

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

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

Custom ServiceContainerModule usage example:

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

The RegisterAssemblyModules extension method is implemented as follows:

public static IServiceContainerBuilder RegisterAssemblyModules(
    [NotNull] this IServiceContainerBuilder serviceContainerBuilder, params Assembly[] assemblies)
{
    #if NET45
        // Solve the problem of asp.net application domain being recycled under IIS
        // 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;
}

Use example

In addition to the change of registration service, there is no difference in use. Take a look at the unit test code

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