AspectJ: custom *.aj file is ignored

Question

Why aspectj-maven-plugin ignore my AnnotationInheritor.aj file? Am I configured something wrong?

I want to advice ItemRepository#getById with custom annotation:

@Repository
public interface ItemRepository extends JpaRepository<Item, Long> {

    // AOP does not work, since autogenerated ItemRepositoryImpl#getById 
    // won't have @MyAnnotation annotation
    @MyAnnotation 
    public Item getById(Long id);
}

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface MyAnnotation {
}

@Aspect
@Component
public class MyAspects {

    @Around("@annotation(MyAnnotation)")
    public Object execute(ProceedingJoinPoint joinPoint) {
        // This advice works correct when @MyAnnotation is placed on class, I tested. 
        // The problem is that I have to put @MyAnnotation on interface method
    }
}

Spring Data JPA use interfaces and Java annotations are never inherited from interface to subclass (due JVM limitations). To make my advice work with custom annotations there is a little AspectJ trick. So as described at previous referrence, I created AnnotationInheritor.aj file:

package com.vbakh.somepackage.aspects;

// For some reason does not work. WHY?
public aspect AnnotationInheritor { 
    declare @method : void ItemRepository+.getById() : @MyAnnotation;
}

And add the following configurations to my pom.xml:

<dependencies>
    ...
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>

    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>1.8.9</version>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.0</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <!-- IMPORTANT -->
                <useIncrementalCompilation>false</useIncrementalCompilation>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>aspectj-maven-plugin</artifactId>
            <version>1.9</version>
            <configuration>
                <complianceLevel>1.8</complianceLevel>
                <source>1.8</source>
                <target>1.8</target>
                <showWeaveInfo>true</showWeaveInfo>
                <verbose>true</verbose>
                <Xlint>ignore</Xlint>
                <encoding>UTF-8 </encoding>
            </configuration>
            <executions>
                <execution>
                    <phase>process-sources</phase>
                    <goals>
                        <goal>compile</goal>
                    </goals>
                </execution>
            </executions>
            <dependencies>
                <dependency>
                    <groupId>org.aspectj</groupId>
                    <artifactId>aspectjtools</artifactId>
                    <version>1.8.10</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

P.S. Is there any way to perform the same logic without *.aj files? Means with *.java files.

Answer 1

I guess it should work, even without AnnotationInheritor

made a small demo, have a look...

demo

Answer 2

I copied your code into an AspectJ project (no Spring or Spring AOP there) in order to test it. I found a few problems:

• @Around("@annotation(MyAnnotation)") will not find the annotation because there is no fully qualified class name.

• declare @method : void ItemRepository+.getById() : @MyAnnotation; does not match your interface method's signature Item getById(Long id).

• MyAspects.execute(..) needs to throw Throwable and of course also return something, such as the result of joinPoint.proceed(). But maybe that was just sloppy copy & paste.

After fixing this, the following MCVE works beautifully:

Helper classes making the project compile:

package de.scrum_master.app;

public class Item {}

package de.scrum_master.app;

public interface JpaRepository<P, Q> {}

package de.scrum_master.app;

import org.springframework.stereotype.Repository;

@Repository
public interface ItemRepository extends JpaRepository<Item, Long> {
  Item getById(Long id);
}

package de.scrum_master.app;

public class ItemRepositoryImpl implements ItemRepository {
  @Override
  public Item getById(Long id) {
    return new Item();
  }
}

Marker annotation:

package de.scrum_master.app;

import java.lang.annotation.*;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface MyAnnotation {}

Driver Application:

package de.scrum_master.app;

public class Application {
  public static void main(String[] args) {
    ItemRepository repository = new ItemRepositoryImpl();
    repository.getById(11L);
  }
}

Aspects:

Just in case you wonder why I added execution(* *(..)) to the pointcut, this is because I wanted to exclude matching call() joinpoints which are available in AspectJ as opposed to Spring AOP.

package de.scrum_master.aspect;

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

@Aspect
@Component
public class MyAspect {
  @Around("@annotation(de.scrum_master.app.MyAnnotation) && execution(* *(..))")
  public Object execute(ProceedingJoinPoint joinPoint) throws Throwable {
    System.out.println(joinPoint);
    return joinPoint.proceed();
  }
}

package de.scrum_master.aspect;

import de.scrum_master.app.Item;
import de.scrum_master.app.ItemRepository;
import de.scrum_master.app.MyAnnotation;

public aspect AnnotationInheritor {
  declare @method : Item ItemRepository+.getById(Long) : @MyAnnotation;
}

Console log:

execution(Item de.scrum_master.app.ItemRepositoryImpl.getById(Long))

Voilà! It works nicely.

If it does not work for you like this you have other issues such as (but not exclusively)

• the "auto-generated ItemRepositoryImpl#getById" you mentioned in passing. Whenever and wherever this is generated during the build process, it needs to exist before the aspect is applied to it. In order to analyze this I would need an MCVE on GitHub, though.

• whether the target code to weave the aspect into is in the same Maven module as the aspect code. If it is not, you need to change your Maven setup.