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To conclude, this is supported if the FactoryBean supports setting a reference to it.
In our case, the osgi:reference returns a collection that cannot be initialized unless all its listeners are specified which cannot be created unless it has the collection it needs injected into it. While we can create the proxy eagerly to allow this there might be some race conditions of services added to the collection that do not get passed on to the listener. I'll take a look at the problem and see whether I can improve the behavior. With Juergen's help I have fixed this.
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Improvement
Resolved
Critical
Need to support circular FactoryBean references for Spring-OSGi
So what needs to be done here is the following: OsgiServiceProxyFactoryBean needs to be able to expose its object early, i.e. even when "getObject()" gets called before the FactoryBean is fully initialized. If it can do that, it will be able to participate in circles. This will work out of the box with Spring 2.0.2 or higher; it is up to OsgiServiceProxyFactoryBean's implementation whether to support that or not.
Spring itself uses that early exposure mechanism for its ListFactoryBean, SetFactoryBean etc already, allowing such collections to be part of a circle. The actual logic for early exposure sits in AbstractFactoryBean, where the FactoryBean exposes a proxy for a given interface in such a case. Any call on that proxy will be delegated to the target object (that the FactoryBean usually builds), with the actual target object obtained on demand (i.e. only when a method call comes in). The actual interface to expose can be determined by the concrete FactoryBean class.
As a consequence, I'm going to move this issue to the Spring OSGi project.
Juergen