As discussed in the sections above, Spring Integration provides a number of endpoints used to interface with external systems, file systems etc. The following is a summary of the various endpoints with quick links to the appropriate chapter.

To recap, Inbound Channel Adapters are used for one-way integration bringing data into the messagng application. Outbound Channel Adapters are used for one-way integration to send data out of the messaging application. Inbound Gateways are used for a bidirectional integration flow where some other system invokes the messaging application and receives a reply. Outbound Gateways are used for a bidirectional integration flow where the messaging application invokes some external service or entity, expecting a result.

In addition, as discussed in Part III, “Core Messaging”, endpoints are provided for interfacing with Plain Old Java Objects (POJOs). As discussed in Section 3.3, “Channel Adapter”, the <int:inbound-channel-adapter> allows polling a java method for data; the <int:outbound-channel-adapter> allows sending data to a void method, and as discussed in Section 7.2, “Messaging Gateways”, the <int:gateway> allows any Java program to invoke a messaging flow. Each of these without requiring any source level dependencies on Spring Integration. The equivalent of an outbound gateway in this context would be to use a Section 7.3, “Service Activator” to invoke a method that returns an Object of some kind.