.NET Core依赖注入集成Dynamic Proxy

在《Castle DynamicProxy基本用法》中介绍了如何将DP与Autofac集成使用,而 .NET Core有自己的依赖注入容器,在不依赖第三方容器的基础上,如何实现动态代理就成了一个问题。

.NET Core依赖注入实现动态代理

我们知道,要创建一个代理对象,需要简单的三步:

.NET Core的依赖注入允许我们自定义ServiceDescriptor对象,而在ServiceDescriptor对象中,我们可以定义对象实例化的过程,这个过程叫做factory,通过自定义factory,我们可以类型的动态代理的创建。

代码如下:

services.AddTransient<LoggingInterceptor>();
services.AddTransient<SampleService>();

services.AddTransient<ISampleService>(provider =>
{
    var target = provider.GetService<SampleService>();
    var loggingInterceptor = provider.GetService<LoggingInterceptor>();
    var proxy = DynamicProxyExtensions.Generator.CreateInterfaceProxyWithTarget<ISampleService>(target, loggingInterceptor);

    return proxy;
});

或者通过实例化ServiceDescriptor的方式进行注入:

services.AddTransient<LoggingInterceptor>();
services.AddTransient<SampleService>();

Func<IServiceProvider, object> factory = (provider) => {
    var target = provider.GetService<SampleService>();
    var loggingInterceptor = provider.GetService<LoggingInterceptor>();
    var auditInterceptor = provider.GetService<AuditInterceptor>().ToInterceptor();
    var proxy = DynamicProxyExtensions.Generator.CreateInterfaceProxyWithTarget<ISampleService>(target, loggingInterceptor, auditInterceptor);

    return proxy;
};
var serviceDescriptor = new ServiceDescriptor(typeof(ISampleService), factory, ServiceLifetime.Transient);

services.Add(serviceDescriptor);

通过这种方式,我们可以将动态代理与依赖注入结合起来。但是这样的代码缺少封装,开发效率偏低,在使用过程中还需要对依赖注入、动态代理都有一定了解,为了解决这些问题,我们需要再次封装。

依赖注入与动态代理的简单封装

public static class DependencyInjectionExtensions
{
    public static IServiceCollection AddService<TService, TImplementation>(this IServiceCollection services,
        ServiceLifetime lifetime, params Type[] interceptorTypes)
    {
        return services.AddService(typeof(TService), typeof(TImplementation), lifetime, interceptorTypes);
    }

    public static IServiceCollection AddService(this IServiceCollection services, Type serviceType, Type implType,
        ServiceLifetime lifetime, params Type[] interceptorTypes)
    {
        services.Add(new ServiceDescriptor(implType, implType, lifetime));
        
        Func<IServiceProvider, object> factory = (provider) =>
        {
            var target = provider.GetService(implType);

            List<IInterceptor> interceptors = interceptorTypes.ToList().ConvertAll<IInterceptor>(interceptorType =>
            {
                return provider.GetService(interceptorType) as IInterceptor;
            });

            var proxy = DynamicProxyExtensions.Generator.CreateInterfaceProxyWithTarget(serviceType, target, interceptors.ToArray());

            return proxy;
        };
        var serviceDescriptor = new ServiceDescriptor(serviceType, factory, lifetime);
        services.Add(serviceDescriptor);

        return services;
    }
}

在使用时需要注意,一定要先将Interceptor类注入到容器中。

.NET Core依赖注入集成Dynamic Proxy

全文结束