学习之路-Asp.core依赖注入(DI源码)学习1.0
首先声明英语好的人一定要学习源码,比较好理解。本人英语渣渣,学习比较慢
为什么要学习DI源码,因为本人写了个AOP组件,需要集成到DI。遇到了难题,所以先学DI源码,学习源码主要学习设计者的思维方式
下来步入正题在github下载源码地址 https://github.com/aspnet/DependencyInjection
首先要学习标准也就是接口。才能明白其设计原理如下图
![](https://img2020.cnblogs.com/blog/2215128/202011/2215128-20201116230633161-1444763899.png)
主要有5个接口
public interface IServiceCollection : IList<ServiceDescriptor>
{
}
这个接口简单定义了一个容器,容器里里面存放ServiceDescriptor(中文服务描述符)
/// <summary>
/// Initializes a new instance of <see cref="ServiceDescriptor"/> with the specified <paramref name="factory"/>.
/// </summary>
/// <param name="serviceType">The <see cref="Type"/> of the service.</param>
/// <param name="factory">A factory used for creating service instances.</param>
/// <param name="lifetime">The <see cref="ServiceLifetime"/> of the service.</param>
public ServiceDescriptor(
Type serviceType,
Func<IServiceProvider, object> factory,
ServiceLifetime lifetime)
: this(serviceType, lifetime)
{
if (serviceType == null)
{
throw new ArgumentNullException(nameof(serviceType));
}
if (factory == null)
{
throw new ArgumentNullException(nameof(factory));
}
ImplementationFactory = factory;
}
这个就是这个类的构造也很简单,从字面理解一个服务的描述者 里面用组合的思想包含了 serviceType(服务类型) lifetime(声明周期),以及一个委托类型工厂IserviceProvider(服务的供应商)
其实英语好了理解这个真的简单,至于这里为什么要用委托工厂暂时没有明白
现在看看这个接口虽然没有声明任何规范,但她继承 IList接口,符合他的规范 增加,删除,查询的规范。
感觉虽然接口简单 但是这个抽象的真的好,设计者以及达到对接口抽象大成了
/// <summary> /// Provides an extension point for creating a container specific builder and an <see cref="IServiceProvider"/>. /// </summary> public interface IServiceProviderFactory<TContainerBuilder> --这是泛型接口
{
/// <summary>
/// Creates a container builder from an <see cref="IServiceCollection"/>.
/// </summary> /// <param name="services">The collection of services</param>
/// <returns>A container builder that can be used to create an <see cref="IServiceProvider"/>.</returns>
TContainerBuilder CreateBuilder(IServiceCollection services);
从中可用创出一个容器生成器,DI的默认实现就是用这个接口规范什么都没干只返回参数。的具体的作用好处暂时还不能体会
/// <summary>
/// Creates an <see cref="IServiceProvider"/> from the container builder.
/// </summary> /// <param name="containerBuilder">The container builder</param>
/// <returns>An <see cref="IServiceProvider"/></returns>
IServiceProvider CreateServiceProvider(TContainerBuilder containerBuilder);
提供一个服务供应商 ,没什么说的
这个接口的中文含义 服务供应商的工厂类型。工厂的作用主要是干什么?为什么要这样设计欢迎大家套论
}
public interface IServiceScope : IDisposable
{
/// <summary>
/// The <see cref="System.IServiceProvider"/> used to resolve dependencies from the scope.
/// </summary>
IServiceProvider ServiceProvider { get; }
}
public interface IServiceScopeFactory
{
/// <summary>
/// Create an <see cref="Microsoft.Extensions.DependencyInjection.IServiceScope"/> which
/// contains an <see cref="System.IServiceProvider"/> used to resolve dependencies from a
/// newly created scope.
/// </summary>
/// <returns>
/// An <see cref="Microsoft.Extensions.DependencyInjection.IServiceScope"/> controlling the
/// lifetime of the scope. Once this is disposed, any scoped services that have been resolved
/// from the <see cref="Microsoft.Extensions.DependencyInjection.IServiceScope.ServiceProvider"/>
/// will also be disposed.
/// </returns>
IServiceScope CreateScope();
}
/// <summary>
/// Optional contract used by <see cref="ServiceProviderServiceExtensions.GetRequiredService{T}(IServiceProvider)"/>
/// to resolve services if supported by <see cref="IServiceProvider"/>.
/// </summary>
public interface ISupportRequiredService
{
/// <summary>
/// Gets service of type <paramref name="serviceType"/> from the <see cref="IServiceProvider"/> implementing
/// this interface.
/// </summary>
/// <param name="serviceType">An object that specifies the type of service object to get.</param>
/// <returns>A service object of type <paramref name="serviceType"/>.
/// Throws an exception if the <see cref="IServiceProvider"/> cannot create the object.</returns>
object GetRequiredService(Type serviceType);
}
还有一个隐藏的重要接口
//
// 摘要:
// Defines a mechanism for retrieving a service object; that is, an object that
// provides custom support to other objects.
public interface IServiceProvider
{
//
// 摘要:
// Gets the service object of the specified type.
//
// 参数:
// serviceType:
// An object that specifies the type of service object to get.
//
// 返回结果:
// A service object of type serviceType. -or- null if there is no service object
// of type serviceType.
object GetService(Type serviceType);
}