java - 基本 AOP 程序抛出 BeanCurrentlyInCreationException

Question

我正在创建一个简单的 AOP 程序并开始获取 BeanCurrentlyInCreationException 异常。

这是我的代码:

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");
    }
}

计算器.java

package program;

import org.springframework.stereotype.Component;

@Component
public class Calculator {

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

配置.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 - 它包含主程序:

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);
    }
}

如果我运行我的程序，我会得到这个异常:

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)

根据我的程序，我没有任何循环依赖，那么是什么导致了这个异常。

另外，如果我对我的代码做一些小改动，那么它工作正常。以下是我为使其正常工作所做的更改:

1)注释Config.java代码中的bean声明:

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

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

}

像这样在我的方面类上启用 @Component 注释:

@Aspect
@Component
public class MyAspect {

    // same as earlier code.
}

Answer 1

我尝试使用帖子中提到的同一段代码，并在 Config.java 中定义了 Bean，它对我有用。我在使用这个程序时遇到的唯一错误是在 MyAspect 类中

'advice must be public'

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

休息执行得很好。您也可以在使用

之前通过刷新上下文来尝试以前的代码

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