Asp.Net Core轻量级Aop解决方案:AspectCore

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AbstractInterceptorAttribute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 : AbstractInterceptorAttribute 
    {
        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");
            }
         }
     }
  • 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...");
        }
    }
  • 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.AddDynamicProxy(); return services.BuildAspectCoreServiceProvider(); }
  • 拦截器配置。

    全局拦截器。使用AddDynamicProxy(Action<IAspectConfiguration>)的重载方法,其中IAspectConfiguration提供Interceptors注册全局拦截器:

     services.AddDynamicProxy(config =>
     {
          config.Interceptors.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 : AbstractInterceptorAttribute 
    {
        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.AddDynamicProxy(config =>
    {
         config.Interceptors.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.AddDynamicProxy(config =>
    {
        config.Interceptors.AddServiced<CustomInterceptorAttribute>();
    });

    作用于特定ServiceMethod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.AddDynamicProxy(config =>
    {
        config.Interceptors.AddTyped<CustomInterceptorAttribute>(method => method.DeclaringType.Name.EndsWith("Service"));
    });
    使用通配符的特定全局拦截器:
    services.AddDynamicProxy(config => { config.Interceptors.AddTyped<CustomInterceptorAttribute>(Predicates.ForService("*Service")); });
  • 在AspectCore中提供NonAspectAttribute来使得ServiceMethod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.AddDynamicProxy(config =>
      {
          //App1命名空间下的Service不会被代理
          config.NonAspectPredicates.AddNamespace("App1");
    
          //最后一级为App1的命名空间下的Service不会被代理
          config.NonAspectPredicates.AddNamespace("*.App1");
    
          //ICustomService接口不会被代理
          config.NonAspectPredicates.AddService("ICustomService");
    
          //后缀为Service的接口和类不会被代理
          config.NonAspectPredicates.AddService("*Service");
    
          //命名为Query的方法不会被代理
          config.NonAspectPredicates.AddMethod("Query");
    
          //后缀为Query的方法不会被代理
          config.NonAspectPredicates.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.Injector.FromContainerAttribute]特性,即可自动注入该属性,如:

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

有问题反馈

如果您有任何问题,请提交 Issue 给我们。
AspectCore Project 项目地址: https://github.com/dotnetcore/AspectCore-Framework
AspectCore Group QQ群: 306531723

posted @ 2017-06-06 00:22  竹韵悠扬丶  阅读(...)  评论(... 编辑 收藏