Spring AOP引入功能报错：找不到concert.PerformanceImp类型合格Bean

Hey there! Let's figure out why you're getting that NoSuchBeanDefinitionException when trying to implement Spring AOP introductions.

The Root Cause #

The core issue lies in how Spring AOP creates proxies by default. When you use @EnableAspectJAutoProxy, Spring defaults to JDK dynamic proxies—which are interface-based. That means the bean in your application context isn't an instance of PerformanceImp; it's a proxy object that implements the Performance interface (and Encoreable, thanks to your introduction logic). So when you try to fetch the bean using PerformanceImp.class, Spring can't locate a bean of that exact class type.

Solutions #

Here are two ways to fix this:

Solution 1: Fetch the Bean by Its Interface (Recommended) #

This follows Spring's best practice of programming to interfaces. Modify your Main class to retrieve the bean via the Performance interface, then cast it to Encoreable:

package concert;

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

public class Main {
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(ConcertConfig.class);
        Performance performance = context.getBean(Performance.class);
        // Cast to Encoreable since the proxy implements this interface
        ((Encoreable) performance).performEncore();
        performance.perform();
    }
}

Solution 2: Force CGLIB Proxying (Class-Based Proxies) #

If you absolutely need to work directly with the PerformanceImp class, you can tell Spring to use CGLIB proxies instead of JDK dynamic proxies. Update your ConcertConfig by adding proxyTargetClass = true to the @EnableAspectJAutoProxy annotation:

package concert;

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

@Configuration
@EnableAspectJAutoProxy(proxyTargetClass = true) // Enable class-based proxies
@ComponentScan("concert")
public class ConcertConfig { }

With this change, Spring creates a subclass proxy of PerformanceImp, so your original Main code will work as intended. Just note that CGLIB can't proxy final classes or methods, so ensure your target class/methods aren't marked as final.

内容的提问来源于stack exchange，提问作者Meninx - メネンックス