Outbox: Information regarding accessing outboxed services (#725)

* added information regarding outboxed services: they're java proxy objects * Apply suggestions from code review Co-authored-by: Marc Becker <[email protected]> * Changes after review * Update java/outbox.md --------- Co-authored-by: Marc Becker <[email protected]>
cap-js · Mar 7, 2024 · e5dd25e · e5dd25e
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@@ -161,6 +161,10 @@ All calls to `CqnService.run` methods return null since they're executed asynchr
 A service wrapped by an outbox can be unboxed by calling the API `OutboxService.unboxed(Service)`. Method calls to the unboxed
 service are executed synchronously without storing the event in an outbox.
 
+::: warning Java Proxy
+A service wrapped by an outbox is a [Java Proxy](https://docs.oracle.com/javase/8/docs/technotes/guides/reflection/proxy.html). Such a proxy only implements the _interfaces_ of the object it is wrapping. This means an outboxed service proxy can't be casted to the class implementing the underlying service object.
+:::
+
 ::: tip Custom outbox for scaling
 The default outbox services can be used for outboxing arbitrary CAP services. If you detect a scaling issue,
 you can define custom outboxes that can be used for outboxing.