The integration layer is typically where we talk to other applications. There might be other applications exposing SOAP or RESTful services over HTTP (the web) or MQ:

• Spring JMS is typically used to send or receive messages on queues or service buses.
• Spring MVC RestTemplate can be used to invoke RESTful services.
• Spring WS can be used to invoke SOAP-based web services.

• Spring Integration provides a higher level of abstraction for building enterprise integration solutions. It enables testability with a clear separation of concerns between the application and integration code. It supports all popular enterprise integration patterns. We will discuss more about Spring Integration in Chapter 10, Spring Cloud Data Flow.