CODEWITHSUNDEEP
javaaopaspectj
Mopparthy Ravindranath
Mopparthy Ravindranath

Reputation: 3328

AspectJ: How to get accessed field's value in a get() pointcut

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

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);
}

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???>);
}

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 to anyone helping me out on this.

Upvotes: 3

Views: 6715

Answers (1)

kriegaex
kriegaex

Reputation: 67457

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:

Driver application:

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;
    }
}

Aspect:

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);
    }
}

Console output:

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

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

Upvotes: 9

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