java - Basic AOP program throws BeanCurrentlyInCreationException

Question

I am creating a simple AOP program and starting getting BeanCurrentlyInCreationException exception with it.

Here is my code:

MyAspect.java

package aspect;

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

@Aspect
//@Component
public class MyAspect {

    @Pointcut("execution(public * *(..))")
    private void anyPublicOperation() {
    }

    @Before("anyPublicOperation()")
    private void beforePointCut(){
        System.out.println("Inside before pointcut of MyAspect");
    }
}

Calculator.java

package program;

import org.springframework.stereotype.Component;

@Component
public class Calculator {

    public int add(int i, int j) {
        return i + j;
    }
}

Config.java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

import aspect.MyAspect;


@Configuration
//Enable AspectJ auto proxying
@EnableAspectJAutoProxy
@ComponentScan(basePackages={"program"})
public class Config {

    //Declare a bean
    @Bean
    public MyAspect aspect() {
        return new MyAspect();
    }
}

App.java - It contains the main program:

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import program.Calculator;

public class App {
    public static void main(String[] args) throws Exception {

        ApplicationContext ctx = new AnnotationConfigApplicationContext(Config.class);

        System.out.println("=======Calling methods========");

        Calculator cal = ctx.getBean(Calculator.class);
        int result = cal.add(10,20);
        System.out.println(result);
    }
}

If I run my program, I am getting this exception:

Aug 13, 2015 2:44:10 PM org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@17ab5d6d: startup date [Thu Aug 13 14:44:10 IST 2015]; root of context hierarchy
Aug 13, 2015 2:44:10 PM org.springframework.context.annotation.AnnotationConfigApplicationContext refresh
WARNING: Exception encountered during context initialization - cancelling refresh attempt
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'aspect' defined in Config: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [aspect.MyAspect]: Factory method 'aspect' threw exception; nested exception is org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'aspect': Requested bean is currently in creation: Is there an unresolvable circular reference?
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:599)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1111)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1006)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:476)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:303)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:299)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:755)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:757)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:480)
    at org.springframework.context.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
    at App.main(App.java:10)

As per my program I do not have any circular dependency, then what is causing this exception.

Also if I do small changes to my code, then it is working fine. Here are the changes that I have done to make it work:

1) Commented the bean declaration in Config.java code:

@Configuration
//Enable AspectJ auto proxying
@EnableAspectJAutoProxy
@ComponentScan(basePackages={"aspects","program"})
public class Config {

    // bean declaration is removed here and updated basePackages for @ComponentScan

}

Enabled @Component annotation on my aspect class like this:

@Aspect
@Component
public class MyAspect {

    // same as earlier code.
}

Answer 1

I tried with the same piece of code mentioned in the post and defined the Bean in Config.java and it worked for me. The only error i got using this program is in the MyAspect class the

'advice must be public'

@Before("anyPublicOperation()")
public void beforePointCut(){
    System.out.println("Inside before pointcut of MyAspect");
}

Rest executed fine. Also you could try the previous code by refreshing the context before using

ApplicationContext context = new AnnotationConfigApplicationContext();
((AnnotationConfigApplicationContext) context).register(Config.class);
((AbstractApplicationContext) context).refresh();