Cyclic references in context xml

[Robert Mark Bram]

Hi All!

When writing a Spring context, are cyclic references handled?

For example,

Java:
A a;
B b;
a.b = b;
b.a = a;

Spring context:
<bean id="a">
<property name="b"><ref local="b"/></property>
</bean>

<bean id="b">
<property name="a"><ref local="a"/></property>
</bean>

If they are not handled, is there a workaround to allow this setup?

Thanks for any advice!

Rob

[vjao]

Hello Rob,

you need to create a third class, let's call it C, that uses both class A and B. Then you just have to use C and you can break the cyclic reference between A and B.

Java :
A a;
B b;
C c;

C.a = a;
C.b = b;

C.doSomethingWithAandB(...);

Hope this help,

Vincent

[viulian]

Exactly the question I was right now looking an answer for [i know topic is old]

I have an 'email' service and an 'errors' service. 'email' can post smtp errors to the 'errors' service, but 'errors' service can send various other errors via email. So I was wondering about the cyclic references.

As right now I'm still wondering if and what the class 'C' might be, I still find one of the question unanswered.
Are cyclic references handled by Spring or not ?

[Andrei Stefan]

http://static.springframework.org/sp...ctor-injection
there is a small text-box called "Circular dependencies".

If you have two singleton beans that reference each other, using setter injection then it will work. If those beans are prototypes (non-singleton), then you'll end up with a circular dependency issue.

[Andrei Stefan]

Here's another good explanation for other case of circular dependencies.

[karldmoore]

As Andrei said with setter injection, you might get away with it. I've found Spring to be darn clever in the past at resolving problems like this.

[viulian]

Thanks Andrei, for pointing out those links, you are right. I do not use constructors and application behaves properly.

Basically I did circular dependencies with setter injection and it worked, but now, trying to proxy the services (so I can have transactions and OSIV) made me think twice whether this is a good pattern and sought help.

Spring is smart indeed

[mobin]

Try this link for a solution to circular dependencies, using a custom injector with annotations http://forum.springframework.org/showthread.php?t=41138&highlight=circular+dependen cy