AspectJ - 使用类型间声明创建全局日志记录器字段 [英] AspectJ - Creating a global Logger field using an Inter-Type Declaration

问题描述

我想创建一个Inter-Type声明，在每个类中声明一个（静态final）Logger实例。

I'd like to create an Inter-Type declaration that declares a (static final) Logger instance inside each class.

构造函数应该传递封闭类 Klazz.class value：

The constructor should be passed the enclosing class Klazz.class value:

@Aspect
public class LoggerAspect {

    public interface Logger {
    }

    public static class LoggerImpl implements Logger {
        private static final Logger logger = 
          new Logger(thisJoinPoint.getTarget().getClass()/*.getName()*/);
    }

    @DeclareParents(value="com.my.api..*",defaultImpl=LoggerImpl.class)
    private Logger implementedInterface;
}

我写了上面的解决方案，但是我不能使用 thisJoinPoint 以外的AspectJ 建议。

I wrote the above solution, however I'm unable to use thisJoinPoint outside of an AspectJ advice.

如果Logger默认实现应用于某些类Klazz，我如何修改上面的代码以成功传递Klazz.class到Logger构造函数？

If the Logger default implementation is applied to some class Klazz, how can I modify the above code to successfully pass Klazz.class to the Logger constructor?

推荐答案

您可以通过类型间声明在任何单个类上声明一个静态成员：

You can declare a static member on any single class via inter-type declaration:

public aspect LoggingAspect {
    static Logger MyClass.someField = Logger.getLogger(MyClass.class.getName());
}

但这不是很灵活，因为你需要为每个单独的类。我只想提一下。

But this is not very flexible because you need to do it for each single class. I just wanted to mention it.

为了添加一些技术上不是但实际上是一个类的静态成员的东西，只需为你的日志方面使用每个类型的关联：

In order to add something which is not technically but effectively a static member to a class, just use per-type association for your logging aspect:

public aspect LoggingAspect
    pertypewithin(org.foo..*)              // per-type association
{
    Logger logger;

    after() : staticinitialization(*) {    // run 1x after class-loading
        logger = Logger.getLogger(
            getWithinTypeName()            // type associated with aspect instance
        );
    }

    pointcut logged() :                    // what to log, e.g. public methods
        execution(public * *(..));         // (pointcut could also be abstract
                                           // and refined in sub-aspects)

    before() : logged() {
        logger.log(...);                   // logging action
    }
}

它是一种常见模式 - 可以在Ramnivas Laddad的优秀书 AspectJ in action（第2版），第6.2章.4。在 AspectJ文档中也有提及。

An example similar to this one - it is a common pattern - can be found in Ramnivas Laddad's excellent book AspectJ in action (2nd edition), chapter 6.2.4. It is also mentioned in the AspectJ documentation.

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