Spring - AOP: @within Exception: java.lang.IllegalArgumentException: error Type referred to is not an annotation type

Question

I'm new to AOP and AspectJ. I'm trying to write a custom logic around a custom annotation with element type TYPE. I also want to use the parameters under my annotation to write a custom logic inside the around method. I'm getting the below mentioned error. I tried reading multiple sources, and most of the sources are related to using @annotation. I'm finding hard to understand the same. Can someone explain, why the following way with @within didn't work with some clear example?

Annotation(Slf4jTrace.java):

package io.ud.project.falcon.logging;

import io.ud.project.falcon.logging.generator.AbstractLogTraceIdGenerator;
import io.ud.project.falcon.logging.generator.DefaultLogTraceIdGenerator;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface Slf4jTrace {

    String traceKey() default "traceId";

    Class<? extends AbstractLogTraceIdGenerator> traceValueGenerator() default DefaultLogTraceIdGenerator.class;

}

Aspect Component(Slf4jTraceAspect.java):

package io.ud.project.falcon.logging;

import lombok.extern.slf4j.Slf4j;
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;

@Aspect
@Component
@SuppressWarnings("unused")
@Slf4j
public class Slf4jTraceAspect {

    @Pointcut("execution(public * *(..))")
    public void publicOperation() {
        //Using this pointcut annotation for Around method.
    }

    @Around(value = "@within(slf4jTrace) && publicOperation()")
    public void logTrace(ProceedingJoinPoint joinPoint, Slf4jTrace slf4jTrace) throws Throwable {
        //Custom logic that uses slf4jTrace's parameters        
        joinPoint.proceed();
        //Custom logic that uses slf4jTrace's parameters
    }
}

Annotated class(Foo.java):

package io.ud.project.falcon.logging;

import io.ud.project.falcon.logging.Slf4jTrace;

@Slf4jTrace(traceKey = "auditID")
public class Foo {

    public void doSomething() {
        //Something happens here.
    }

}

Error on application startup:

, 2021-01-02 22:16:41,340, ERROR [main] o.s.b.SpringApplication.reportFailure(833) | Application run failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'objectMapperConfigurer' defined in springfox.documentation.spring.web.SpringfoxWebMvcConfiguration
: BeanPostProcessor before instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.transaction.annotation.ProxyTransactionManagementConfiguration': BeanPostProcessor before instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.cache.annotation.ProxyCachingConfiguration': Initialization of bean failed; nested exception is java.lang.IllegalArgumentException: error Type referred to is not an annotation type: slf4jTrace
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:497)
        at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:312)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:310)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:205)
        at org.springframework.context.support.PostProcessorRegistrationDelegate.registerBeanPostProcessors(PostProcessorRegistrationDelegate.java:238)
        at org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:709)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:534)
        at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140)
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:752)
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:388)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:327)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1246)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1234)
        at io.ud.project.falcon.FalconApplication.main(FalconServiceApplication.java:65)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
        at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)

Answer 1

I did not try to run your code, but two things I immediately noticed when glancing at it:

• BeanCreationException for internal Spring types often occur if aspect pointcuts are too broad, i.e. aspects are also woven into (even if not executed in) Spring classes. In such cases you want to limit the aspect scope by adding something like ... && within(my.package..*) to your pointcut. Alternatively, if your aspect is in a library potentially running against unknown package names you can exclude the Spring packages or classes causing problems by !within(org.springframework..*) or whatever package names are applicable in your case. See also my answer here.

• Your @Around advice returns void, i.e. it will also only match void methods, which probably is not what you want. In order to match non-void methods, the advice must return something other than void, usually just Object if you want to match any return type. Also make sure that you return the result of proceed() or whatever other result you want to be returned.