AspectJ：如何在get（）切入点中获取访问字段的值 [英] AspectJ: How to get accessed field's value in a get() pointcut

问题描述

我正在编写一个方面记录器来在访问给定类中的任何成员变量时写入日志。

I am writing an aspect logger to write a log whenever any member variable in a given class is accessed.

如果我为单个变量写一个特定的切入点，如下面，我能够得到该字段的值。

If I write a specific pointcut for a single variable like below, I am able to get the value of the field.

@Pointcut("get(* abc.ThreadPoolService.drMaxTh)")
public void drFields() {}

@AfterReturning(pointcut="drFields()", returning="drMaxTh")  
public void afterAccessingdrFields(int drMaxTh) {
    LOGGER.info("Accessed the field drMaxTh " + drMaxTh);
}

但是我的课有十几个+变量，我不打算写每个人的特定切入点。所以，我想写类似的东西..

But my class has a dozen+ variables, and I don't intend on writing specific pointcuts for each of them. So, I want to write something like..

@Pointcut("get(* abc.ThreadPoolService.*)")
public void drFields() {}

@AfterReturning(pointcut="drFields()", returning= **????** )  
public void afterAccessingdrFields(what should come here???) {
    LOGGER.info("Accessed the field drMaxTh " + <and here???>);
}

但无法理解如何捕获字段的名称和值在通配符字段访问说明符的情况下被访问。

But unable to understand how to capture the name and value of the field that is being accessed, in case of a wildcard field access specifier.

Thanx给任何帮助我的人。

Thanx to anyone helping me out on this.

推荐答案

实际上非常简单， sheltem 是对的，你可以在返回时使用 Object 类型声明。这是一个小小的演示，表明它甚至适用于静态和非静态成员，只要它们未被声明 final ：

It is actually very simple, and sheltem was right, you can just use Object in the returning type declaration. Here is a little demo showing that it even works for both static and non-static members, as long as they are not declared final:

驱动程序应用程序：

package de.scrum_master.app;

public class Application {
    public static final double PI = Math.PI;
    static String producer = "Scrum-Master.de";

    private int id = 11;
    private String author = "Alexander Kriegisch";
    private final String COUNTRY = "Germany";

    public static void main(String[] args) {
        Object dummy;
        Application application = new Application();

        // Access static fields
        dummy = PI;
        dummy = producer;
        // Access non-static fields
        dummy = application.author;
        dummy = application.id;
        dummy = application.COUNTRY;
    }
}

看点

package de.scrum_master.aspect;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;

@Aspect
public class FieldAccessLogger {
    @Pointcut("get(* de.scrum_master.app.Application.*)")
    public void fieldAccess() {}

    @AfterReturning(pointcut = "fieldAccess()", returning = "field")
    public void afterFieldAccess(Object field, JoinPoint thisJoinPoint) {
        System.out.println(thisJoinPoint.toLongString());
        System.out.println("  " + thisJoinPoint.getSignature().getName());
        System.out.println("  " + field);
    }
}

控制台输出：

get(static java.lang.String de.scrum_master.app.Application.producer)
  producer
  Scrum-Master.de
get(private java.lang.String de.scrum_master.app.Application.author)
  author
  Alexander Kriegisch
get(private int de.scrum_master.app.Application.id)
  id
  11

如您所见， PI 和 COUNTRY 未被拦截，因为它们是（最终）常量。

As you can see, PI and COUNTRY are not intercepted because they are (final) constants.

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