Abstraction and loose coupling is always desired. Messaging gateways is a mechanism to publish a contract that can be used by systems without exposing the underlying messaging implementation. For example, a gateway for a mailing subsystem can expose methods for sending and receiving mail. Internally, the implementation can be done using the raw Java mail API, or can be adapters from Spring Integration, or may be some custom implementation altogether. As long as the contract does not change, implementation can be easily switched or enhanced without impacting on the rest of the modules. It is an implementation of more generic gateway patterns. Gateways can be of two types: synchronous and asynchronous.

<int:gateway id="feedService" 
  service-interface="com.cpandey.siexample.service.FeedService" 
  default-request-channel...