如何在Spring中为（非静态）内部类定义bean？ 避免循环依赖

Question

I am having a class with an inner class like this:

package myPackage;

public class A {
    private B b;

    public void setB(B b) { this.b = b; }
    public B getB() { return this.b; }

    public class B {
    }
}

And I have my spring configuration as follow:

<bean id="a" class="myPackage.A" autowire="byName" scope="prototype">
    <property name="b">
        <bean class="myPackage.A$B" name="b" autowire="byName" scope="prototype">
            <constructor-arg ref="a"/>
        </bean>
    </property>
</bean>

But I am facing this error:

org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'a': Requested bean is currently in creation: Is there an unresolvable circular reference?

Of course it is obvious that I am having a circular reference, but how can I have a spring bean for my inner class?

Answer 1

I'm not sure this can be resolved at the Spring level if you need a to be scoped as prototype. The issue is that you're trying to create an instance of a , which requires a reference to a b , which in turn is referencing a different instance of a (because prototype gives you a new instance every time you inject the bean), and so on. If what you really want is for the a to be a prototype bean containing a b that refers to the same enclosing instance of a then you'll have to use Java config or a factory bean.