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NET Core的AOP实施方法1 DispatchProxy
NET Framework的AOP实施方法1 ContextBoundObject
NET Framework的AOP实施方法2 RealProxy

源码见Github

DispatchProxy

NET Core
DispatchProxy 是一个在 .NET 框架中引入的概念，特别是在 C# 语言中。它是一种特殊类型的代理，用于在运行时动态地分派方法调用到不同的实现。DispatchProxy 类位于 System.Runtime.Remoting.Proxies 命名空间中，并且是 RealProxy 类的一个派生类。

以下是 DispatchProxy 的一些关键点：

动态分派：DispatchProxy 允许开发者在运行时决定将方法调用分派给哪个对象。这使得可以在不修改现有代码的情况下，动态地改变对象的行为。

透明代理：DispatchProxy 是一种透明代理，这意味着客户端代码不需要知道代理的存在。客户端代码可以直接调用方法，就像它们直接调用实际对象一样。

类型安全：尽管 DispatchProxy 是动态分派的，但它仍然保持类型安全。代理对象可以被强制转换为任何接口类型，并且只有那些接口上的方法调用才会被分派。

创建自定义代理：开发者可以通过继承 DispatchProxy 类并重写 Invoke 方法来创建自己的代理。在 Invoke 方法中，开发者可以决定如何分派方法调用，例如，基于调用的方法名、参数或其他逻辑。

性能开销：由于 DispatchProxy 涉及到运行时的动态分派，因此可能会有一些性能开销。因此，它更适合于那些性能不是主要关注点的场景。

用途：DispatchProxy 可以用于多种场景，包括但不限于日志记录、性能监控、事务管理、安全性检查、Mock对象的创建等。

相较于RealProxy和ContextBoundObject，DispatchProxy的实现更加便捷

创建日志拦截器

public class LoggingDecorator<T> : DispatchProxy
{private T _decorated;protected override object Invoke(MethodInfo methodInfo, object[] args){try{LogBefore(methodInfo, args);var result = methodInfo.Invoke(_decorated, args);if (methodInfo.IsAsyncMethod()){if (methodInfo.ReturnType == typeof(Task)){var task = (Task)result;var val = InternalAsyncHelper.AwaitTaskWithPostActionAndFinally(task,async () =>{Debug.WriteLine($"Task {methodInfo.Name} completed");}, /*成功时执行*/ex =>{if (ex != null){Debug.WriteLine($"Task {methodInfo.Name} threw an exception: {ex.ToString()}");}});return val;}else{var returnTypeGenericTypeArgument = methodInfo.ReturnType.GenericTypeArguments[0];var val = InternalAsyncHelper.CallAwaitTaskWithPostActionAndFinallyAndGetResult(returnTypeGenericTypeArgument,result,async (o) =>{Debug.WriteLine($"Task {methodInfo.Name} completed with result {o}");}, /*成功时执行*/ex =>{if (ex != null){Debug.WriteLine($"Task {methodInfo.Name} threw an exception: {ex.ToString()}");}});return val;}}else{LogAfter(methodInfo, args, result);}return result;}catch (Exception ex) when (ex is TargetInvocationException){LogException(ex.InnerException ?? ex, methodInfo);throw ex.InnerException ?? ex;}}public static T Create(T decorated){object proxy = Create<T, LoggingDecorator<T>>();((LoggingDecorator<T>)proxy).SetParameters(decorated);return (T)proxy;}private void SetParameters(T decorated){if (decorated == null){throw new ArgumentNullException(nameof(decorated));}_decorated = decorated;}private void LogException(Exception exception, MethodInfo methodInfo = null){Console.WriteLine($"Class {_decorated.GetType().FullName}, Method {methodInfo.Name} threw exception:\n{exception}");}private void LogAfter(MethodInfo methodInfo, object[] args, object result){Console.WriteLine($"Class {_decorated.GetType().FullName}, Method {methodInfo.Name} executed, Output: {result}");}private void LogBefore(MethodInfo methodInfo, object[] args){Console.WriteLine($"Class {_decorated.GetType().FullName}, Method {methodInfo.Name} is executing");}
}

代理异步的帮助类

internal static class InternalAsyncHelper
{public static bool IsAsyncMethod(this MethodInfo method){return method.ReturnType == typeof(Task)|| method.ReturnType.IsGenericType&& method.ReturnType.GetGenericTypeDefinition() == typeof(Task<>);}public static async Task AwaitTaskWithPostActionAndFinally(Task actualReturnValue,Func<Task> postAction,Action<Exception> finalAction){Exception exception = null;try{await actualReturnValue;await postAction();}catch (Exception ex){exception = ex;}finally{finalAction(exception);}}public static async Task<T> AwaitTaskWithPostActionAndFinallyAndGetResult<T>(Task<T> actualReturnValue,Func<object, Task> postAction,Action<Exception> finalAction){Exception exception = null;try{var result = await actualReturnValue;await postAction(result);return result;}catch (Exception ex){exception = ex;throw;}finally{finalAction(exception);}}public static object CallAwaitTaskWithPostActionAndFinallyAndGetResult(Type taskReturnType,object actualReturnValue,Func<object, Task> action,Action<Exception> finalAction){//AwaitTaskWithPostActionAndFinallyAndGetResult<taskReturnType>(actualReturnValue, action, finalAction);return typeof(InternalAsyncHelper).GetMethod("AwaitTaskWithPostActionAndFinallyAndGetResult",BindingFlags.Public | BindingFlags.Static).MakeGenericMethod(taskReturnType).Invoke(null, new object[] { actualReturnValue, action, finalAction });}
}

声明及调用示例

public interface ICalculator
{int Add(int a, int b);Task<int> AddAsync(int a, int b);
}
public class Calculator : ICalculator
{public int Add(int a, int b){//throw new NotImplementedException("This method is not implemented. sorry!");return a + b;}public async Task<int> AddAsync(int a, int b){await Task.Delay(1000);return a + b;}
}

示例

var decoratedCalculator = LoggingDecorator<ICalculator>.Create(new Calculator());
decoratedCalculator.Add(3, 5);
Console.WriteLine($"Started at {DateTime.Now:HH:mm:ss.fff}");
var res =decoratedCalculator.AddAsync(2, 4);Console.WriteLine("Waiting for 1 seconds for querying customer...");
Console.WriteLine($"Querying {DateTime.Now:HH:mm:ss.fff}");
Console.WriteLine(res.GetAwaiter().GetResult());
Console.WriteLine($"Finished at {DateTime.Now:HH:mm:ss.fff}");