How to make pointcut that indicate child class's method call which didn't override parent's method?

Question

There is one interface Foo, having two default methods m1, m2.

There are 3 classes Foo1, Foo2, Foo3 implementing Foo. Foo3 does not override method m1, but Foo1, Foo2 do.

I want to create an aspect which targets Foo3's m1 method.

I tried @Pointcut("bean(foo3) && execution(* *.m1(..)), and it works properly while Spring Boot is running. But when I create a proxy object programmatically for unit testing, it does not work.

I know that bean(foo3) makes it work under Spring Boot, but I cannot find any alternative way to express the pointcut, which still works in the test. How can I make it work in this situation?

public interface Foo {
    default Object m1() {
        // doSomething
        return Something;
    }

    default Object m2() {
        // doSomething
        return Something;
    }
}

public class Foo3 implements Foo {
    // not overriding any method.
}

@Component @Aspect
public class ExampleAspect {
    @Pointcut("bean(foo3) && execution(* *.m1(..))")
    public void exampleAspect() {}

    @Around("exampleAspect()")
    public Object proxyMethod(ProceedingJoinPoint joinPoint) throws Throwable {
        // ...
        Object result = joinPoint.proceed();
        // ...
    }
}

public Foo3Test {
    Foo instance = new Foo3();
    AspectJProxyFactory factory = new AspectJProxyFactory(instance);
    factory.addAspect(new ExampleAspect());
    Foo proxy = factory.getProxy();
    proxy.m1(); // it didn't use proxy. invoke real method.
}

I tried these pointcuts:

• target(Foo3) && execution(* Foo.m1(..)) does not work even under Spring Boot
• within(Foo3) && execution(* Foo.m1(..)) does not work even under Spring Boot
• execution(Foo.m1(..)) works but all m1 methods are proxied

Answer 1

I am not a Spring expert, but in order to make the special Spring AOP pointcut designator bean work, I guess you might need an application context in your test. Hoewever, I understand the need to create quickly running tests without all that ceremony. Fortunately, this is not difficult to achieve. Simply change your pointcut to:

@Pointcut("target(Foo3) && execution(* m1(..))")
public void exampleAspect() {}

I tried, it works beautifully. Here is how I tested it:

package de.scrum_master.spring.q76824399;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.stereotype.Component;

@Component
@Aspect
public class ExampleAspect {
  @Pointcut("target(Foo3) && execution(* m1(..))")
  public void exampleAspect() {}

  @Around("exampleAspect()")
  public Object proxyMethod(ProceedingJoinPoint joinPoint) throws Throwable {
    System.out.println(joinPoint + " -> " + joinPoint.getTarget());
    return joinPoint.proceed();
  }
}

package de.scrum_master.spring.q76824399;

import org.springframework.aop.aspectj.annotation.AspectJProxyFactory;

public class Foo3Test {
  public static void main(String[] args) {
    ExampleAspect aspect = new ExampleAspect();
    Foo[] instances = { new Foo1(), new Foo2(), new Foo3() };
    for (Foo instance : instances) {
      AspectJProxyFactory factory = new AspectJProxyFactory(instance);
      factory.addAspect(aspect);
      Foo proxy = factory.getProxy();
      proxy.m1();
    }
  }
}

And this is the console log:

10:45:11.823 [main] DEBUG org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory - Found AspectJ method: public java.lang.Object de.scrum_master.spring.q76824399.ExampleAspect.proxyMethod(org.aspectj.lang.ProceedingJoinPoint) throws java.lang.Throwable
10:45:12.055 [main] DEBUG org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory - Found AspectJ method: public java.lang.Object de.scrum_master.spring.q76824399.ExampleAspect.proxyMethod(org.aspectj.lang.ProceedingJoinPoint) throws java.lang.Throwable
10:45:12.071 [main] DEBUG org.springframework.aop.aspectj.annotation.ReflectiveAspectJAdvisorFactory - Found AspectJ method: public java.lang.Object de.scrum_master.spring.q76824399.ExampleAspect.proxyMethod(org.aspectj.lang.ProceedingJoinPoint) throws java.lang.Throwable
execution(Object de.scrum_master.spring.q76824399.Foo.m1()) -> de.scrum_master.spring.q76824399.Foo3@6eda5c9

Please note how the aspect finds all 3 instances of Foo1, Foo2, Foo3, but the advice is only triggered for the Foo3 instance.