11.4 Summary

• Reactive programming involves creating pipelines through which data flows.
• The Reactive Streams specification defines four types: Publisher, Subscriber, Subscription, and Transformer (which is a combination of Publisher and Subscriber).
• Project Reactor implements Reactive Streams and abstracts stream definitions into two primary types, Flux and Mono, each of which offers several hundred operations.
• Spring leverages Reactor to create reactive controllers, repositories, REST clients, and other reactive framework support.