With the Envelope Wrapper an incompatible message from an external system is made compatible with our Actor System. Yet, the opposite situation may be true; a message that the local Actor System needs to send is not compatible with an external system because the external system needs more content than the local system stores. What is more, the external system cannot or should not retrieve the extra information it requires. This situation can be resolved by using a Content Enricher.
The basic solution put forth by [Hohpe & Woolf] uses another component—in our case, an Actor—to enrich the content of the message before it is sent on to the external system, such that the message will contain all the content needed by that system once it is delivered.
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The full text is now available as part of my book Reactive Enterprise with Actor Model on Safari Books Online.
