如何使用 Castle Core 或其他库(只是免费库)为横切关注点编写拦截器(AOP)

问题描述

我想要一个像这样的属性来处理横切关注点，比如 Logging , Exception , ...

I want to have an attribute like this for Cross Cutting Concerns like Logging , Exception , ...

public class MyService
{

[Log] // Interception (AOP)
[ExceptionHandler] // Interception (AOP)
public void DoSomething()
   {

   }
}

我知道我可以用 postsharp 编写这些代码，但我想用免费的库(如 Castle Core 和 ...

I know that I can write these codes with postsharp but I want to write these interceptions with free libraries like Castle Core and ...

任何人都可以帮助我并为此目的编写示例吗???我需要一个非常简单的样本来学习概念

Can anyone help me and write a sample for these purpose ???I need a very simple sample for learning concepts

推荐答案

Autofac 是一个免费的 IoC 容器.我使用 Autofac 和 Autofac.Extras.DynamicProxy2 nuget, 文档.

Autofac is a free IoC container. I use Autofac with Autofac.Extras.DynamicProxy2 nuget, docs.

假设您知道为什么以及何时(和不)使用拦截器，并且您想拦截某些功能:

Assuming you know why and when to (and not to) use interceptors, and you want to intercept some functionality:

public class FooService : IFooService
{
    public void MoreFoo()
    {
        DoSomething();
    }
    public void LessFoo()
    {
        DoSomethingElse();
    }
}

它需要连线".我喜欢属性，因为您不需要在 IoC 容器接线中明确指定拦截器.您只需指定一个要注意的属性:

It needs to be "wired". I like attributes as you don't need to explicitly specify the interceptor at IoC container wiring. You just specify an attribute to watch out for:

[Intercept(typeof(Logger)]
public class FooService : IFooService { ... }

并接线:

var builder = new ContainerBuilder();
builder.RegisterType<FooService>()
   .EnableClassInterceptors();

然后在另一个文件中创建您的 Logger 拦截器:

Then create your Logger interceptor in another file:

class Logger : IInterceptor
{
    public void Intercept(IInvocation invocation) // implements the IInterceptor interface
    {
        _loggerService.Log("calling " + invocation.Method.Name);
        invocation.Proceed();
        _loggerService.Log("finished " + invocation.Method.Name);
    }
}

如您所见，您可以创建计时器、try-catch 块等等.数据库上下文和其他一次性资源很有趣:

As you can see, you can create timers, try-catch blocks, and much more. Database context and other disposable resources is an interesting one:

class Logger : IInterceptor
{
    public void Intercept(IInvocation invocation) // implements the IInterceptor interface
    {
        using (var someThing = new SomeResource())
        {
            invocation.Proceed();
        }
    }
}

通常对于这样的资源，您需要在方法中使用 someThing.这是另一个问题的主题！(请参阅 invocation.SetArgumentValue 或 invocation.TargetType.GetProperties() 以与封闭类进行通信.我对此不是 100% 满意，因此其他人的一些评论会有所帮助)

Usually with such a resource you need to use someThing inside your method. That's a topic for another question! (see invocation.SetArgumentValue or invocation.TargetType.GetProperties() to communicate to the enclosing class. I'm not 100% comfortable with this, so some comments from others would be helpful)

那么，以日志为例:

void ManageFoo()
{
    // sorry for the messy code, what else can I do?!
    _logger("more foo please");
    _fooService.MoreFoo();
    _logger("less foo please");
    _fooService.LessFoo();
    _logger("enough foo");
}

ManageFoo 方法的实际关注点在所有混乱的日志记录中都消失了(添加安全性和其他问题，您最终可能会遇到大麻烦).

The actual concern of the ManageFoo method is lost in all the mess of logging (add security and other concerns and you can end up with a big mess).

现在你可以像这样重写它:

Now you can rewrite it like this:

void ManageFoo()
{
    _fooService.MoreFoo();
    _fooService.LessFoo();
}

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