#EnableAspectJAutoProxy not work with proxyTargetClass=false - spring-aop

Question

I am learning about Spring AOP at first time.
I am reading about in this sites:
Site2 and
Site1
Following this I have made the next classes
Main class:
public class App {
public static void main(String[] args) {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
context.register(AppConfig.class);
context.refresh();
MessagePrinter printer = context.getBean(MessagePrinter.class);
System.out.println(printer.getMessage());
}
}
App config class:
#Configuration
#ComponentScan("com.pjcom.springaop")
#EnableAspectJAutoProxy(proxyTargetClass=true)
public class AppConfig {
#PostConstruct
public void doAlert() {
System.out.println("Application done.");
}
}
Aspect class:
#Component
#Aspect
public class AspectMonitor {
#Before("execution(* com.pjcom.springaop.message.impl.MessagePrinter.getMessage(..))")
public void beforeMessagePointCut(JoinPoint joinPoint) {
System.out.println("Monitorizando Mensaje.");
}
}
And others...
Just like that app work nice, but if I put proxyTargetClass to false. Then I get the error below.
Exception in thread "main" org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type [com.pjcom.springaop.message.impl.MessagePrinter] is defined
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:318)
at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:985)
at com.pjcom.springaop.App.main(App.java:18)
Why?

Answer 1

#EnableAspectJAutoProxy(proxyTargetClass=false)
Indicates that JDK dynamic proxy will be created to support aspect execution on the object. And therefore as this type of proxy requires a class to implement an interface your MessagePrinter must implement some interface which declares method getMessage.
#EnableAspectJAutoProxy(proxyTargetClass=true)
On the opposite instruct to use CGLIB proxy which is able to create proxy for a class without an interface.

Answer 2

1> Message Printer has to be defined as a component i.e :
`
package com.pjcom.springaop.message.impl;
#Component
public class MessagePrinter{
public void getMessage(){
System.out.println("getMessage() called");
}
}`
in the same package as configuration java file if no #ComponentScan is not defined for some other packages.
2> If same type of bean class has many other dependencies then to resolve dependencies in spring Config use #Qualifier annotation.