Cyclic references via ProxyFactoryBean throw an BeanCreationException [SPR-768]

[spring-projects-issues]

Felix von Delius opened SPR-768 and commented

If You have a cyclic dependency between two components which are intercepted with a ProxyFactoryBean, an BeanCreationException is thrown. Without interceptors, the wireing works.

Here's an example of such a wireing:

<bean id="bla" class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="target">
<bean id="blaTarget" class="wireing.BlaImpl">
<property name="fasl"><ref bean="fasl"></ref></property>
</bean>
</property>
<property name="proxyInterfaces"><value>wireing.Bla</value></property>
<property name="interceptorNames">
<list>
<value>loggingAdvice</value>
</list>
</property>
</bean>

<bean id="fasl"
class="org.springframework.aop.framework.ProxyFactoryBean">
<property name="target">
<bean id="faslTarget" class="wireing.FaslImpl">
<property name="bla"><ref bean="bla"></ref></property>
</bean>
</property>
<property name="proxyInterfaces"><value>wireing.Fasl</value></property>
<property name="interceptorNames">
<list>
<value>loggingAdvice</value>
</list>
</property>
</bean>

A workaround for this issue is to use the <lookup-method name="getBla" bean="bla" /> instead of the property-tag for the dependency.

---

Affects: 1.1.5

[spring-projects-issues]

Juergen Hoeller commented

Actually, this is a known problem. Cyclic dependencies between FactoryBeans are effectively not supported, because they can't be resolved in a straightforward fashion.

Essentially, it's a chicken-and-egg problem: FactoryBean #1 needs to be fully initialized before it can produce an object, but depends on FactoryBean #2 which needs to be fully initialized before it can produce an object too, but in turn depends on FactoryBean #1 again...

There is an argument that cyclic dependencies can always be refactored, moving common logic out into a third object that both of the original objects depend on. This is certainly a good design principle.

We nevertheless support circular references between plain JavaBeans, BTW, just not for FactoryBeans and neither for references that go into constructor arguments.

Juergen

[spring-projects-issues]

Juergen Hoeller commented

We might be able to provide a solution for this at least for specific cases, where ProxyFactoryBean could expose proxy even without fully initialized interceptor chain. To be revisited for Spring 1.3.

Juergen

[spring-projects-issues]

Juergen Hoeller commented

As of Spring 2.0 M2, this should work as well as it possibly can now: If you define ProxyFactoryBeans with the target identified through "targetName" (or the last name in the "interceptorNames" list), the actual proxies will now be initialized lazily on first access. However, strong references expressed through <ref> or an inner bean definition will still lead to initialization failure - only "targetName" will properly work in such a scenario.

Juergen