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浅谈AspectCore_实用技巧

程序员文章站 2022-06-06 15:05:35
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这篇文章主要介绍了Asp.Net Core轻量级Aop解决方案:AspectCore,需要的朋友可以参考下

什么是AspectCore Project ?

AspectCore Project 是适用于Asp.Net Core 平台的轻量级 Aop(Aspect-oriented programming) 解决方案,它更好的遵循Asp.Net Core的模块化开发理念,使用AspectCore可以更容易构建低耦合、易扩展的Web应用程序。AspectCore使用Emit实现高效的动态代理从而不依赖任何第三方Aop库。

开使使用AspectCore

启动 Visual Studio。从 File 菜单, 选择 New > Project。选择 ASP.NET Core Web Application 项目模版,创建新的 ASP.NET Core Web Application 项目。

  • 从 Nuget 安装 AspectCore.Extensions.DependencyInjection package:

  • PM> Install-Package AspectCore.Extensions.DependencyInjection

  • 在一般情况下可以使用抽象的InterceptorAttribute自定义特性类,它实现IInterceptor接口。AspectCore默认实现了基于Attribute的拦截器配置。我们的自定义拦截器看起来像下面这样:


public class CustomInterceptorAttribute : InterceptorAttribute
{
  public async override Task Invoke(IAspectContext context, AspectDelegate next)
  {
    try
    {
      Console.WriteLine("Before service call");
      await next(context);
    }
    catch (Exception)
    {
      Console.WriteLine("Service threw an exception!");
      throw;
    }
    finally
    {
      Console.WriteLine("After service call");
    }
   }
 }

定义ICustomService接口和它的实现类CustomService:


public interface ICustomService
{
  [CustomInterceptor]
  void Call();
}
public class CustomService : ICustomService
{
  public void Call()
  {
    Console.WriteLine("service calling...");
  }
}

在HomeController中注入ICustomService:


public class HomeController : Controller
{
  private readonly ICustomService _service;
  public HomeController(ICustomService service)
  {
    _service = service;
  }
  public IActionResult Index()
  {
    _service.Call();
    return View();
  }
}

注册ICustomService,接着,在ConfigureServices中配置创建代理类型的容器:


public IServiceProvider ConfigureServices(IServiceCollection services)
{
  services.AddTransient<ICustomService, CustomService>();
  services.AddMvc();
  services.AddAspectCore();
  return services.BuildAspectCoreServiceProvider();
}

拦截器配置。首先安装AspectCore.Extensions.Configuration package:


PM> Install-Package AspectCore.Extensions.Configuration

全局拦截器。使用AddAspectCore(Action<AspectCoreOptions>)重载方法,其中AspectCoreOptions提供InterceptorFactories注册全局拦截器:


 services.AddAspectCore(config =>
 {
   config.InterceptorFactories.AddTyped<CustomInterceptorAttribute>();
 });

带构造器参数的全局拦截器,在CustomInterceptorAttribute中添加带参数的构造器:


public class CustomInterceptorAttribute : InterceptorAttribute
{
  private readonly string _name;
  public CustomInterceptorAttribute(string name)
  {
    _name = name;
  }
  public async override Task Invoke(AspectContext context, AspectDelegate next)
  {
    try
    {
      Console.WriteLine("Before service call");
      await next(context);
    }
    catch (Exception)
    {
      Console.WriteLine("Service threw an exception!");
      throw;
    }
    finally
    {
      Console.WriteLine("After service call");
    }
  }
}

修改全局拦截器注册:


services.AddAspectCore(config =>
{
   config.InterceptorFactories.AddTyped<CustomInterceptorAttribute>(args: new object[] { "custom" });
});

作为服务的全局拦截器。在ConfigureServices中添加:


services.AddTransient<CustomInterceptorAttribute>(provider => new CustomInterceptorAttribute("service"));

修改全局拦截器注册:


services.AddAspectCore(config =>
{
  config.InterceptorFactories.AddServiced<CustomInterceptorAttribute>();
});

作用于特定Service或Method的全局拦截器,下面的代码演示了作用于带有Service后缀的类的全局拦截器:


services.AddAspectCore(config =>
{
  config.InterceptorFactories.AddTyped<CustomInterceptorAttribute>(method => method.DeclaringType.Name.EndsWith("Service"));
});

使用通配符的特定全局拦截器:


services.AddAspectCore(config =>
{
  config.InterceptorFactories.AddTyped<CustomInterceptorAttribute>(PredicateFactory.ForService("*Service"));
});

在AspectCore中提供NonAspectAttribute来使得Service或Method不被代理:


[NonAspect]
public interface ICustomService
{
  void Call();
}

同时支持全局忽略配置,亦支持通配符:


 services.AddAspectCore(config =>
 {
   //App1命名空间下的Service不会被代理
   config.NonAspectOptions.AddNamespace("App1");
   //最后一级为App1的命名空间下的Service不会被代理
   config.NonAspectOptions.AddNamespace("*.App1");
   //ICustomService接口不会被代理
   config.NonAspectOptions.AddService("ICustomService");
   //后缀为Service的接口和类不会被代理
   config.NonAspectOptions.AddService("*Service");
   //命名为Query的方法不会被代理
   config.NonAspectOptions.AddMethod("Query");
   //后缀为Query的方法不会被代理
   config.NonAspectOptions.AddMethod("*Query");
 });

拦截器中的依赖注入。在拦截器中支持属性注入,构造器注入和服务定位器模式。
属性注入,在拦截器中拥有public get and set权限的属性标记[AspectCore.Abstractions.FromServices](区别于Microsoft.AspNetCore.Mvc.FromServices)特性,即可自动注入该属性,如:


public class CustomInterceptorAttribute : InterceptorAttribute
{
  [AspectCore.Abstractions.FromServices]
  public ILogger<CustomInterceptorAttribute> Logger { get; set; }
  public override Task Invoke(AspectContext context, AspectDelegate next)
  {
    Logger.LogInformation("call interceptor");
    return next(context);
  }
}

构造器注入需要使拦截器作为Service,除全局拦截器外,仍可使用ServiceInterceptor使拦截器从DI中激活:


public interface ICustomService
{
  [ServiceInterceptor(typeof(CustomInterceptorAttribute))]
  void Call();
}

服务定位器模式。拦截器上下文AspectContext可以获取当前Scoped的ServiceProvider:


public class CustomInterceptorAttribute : InterceptorAttribute
{
  public override Task Invoke(AspectContext context, AspectDelegate next)
  {
    var logger = context.ServiceProvider.GetService<ILogger<CustomInterceptorAttribute>>();
    logger.LogInformation("call interceptor");
    return next(context);
  }
}

使用Autofac和AspectCore。AspectCore原生支持集成Autofac,我们需要安装下面两个nuget packages:


PM> Install-Package Autofac.Extensions.DependencyInjection
PM> Install-Package AspectCore.Extensions.Autofac

AspectCore提供RegisterAspectCore扩展方法在Autofac的Container中注册动态代理需要的服务,并提供AsInterfacesProxy和AsClassProxy扩展方法启用interface和class的代理。修改ConfigureServices方法为:


public IServiceProvider ConfigureServices(IServiceCollection services)
{
  services.AddMvc();
  var container = new ContainerBuilder();
  container.RegisterAspectCore();
  container.Populate(services);
  container.RegisterType<CustomService>().As<ICustomService>().InstancePerDependency().AsInterfacesProxy();

  return new AutofacServiceProvider(container.Build());
}

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