AspectJ: custom *.aj file is ignored

问题

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.

回答1:

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.