Reactive Systems are Responsive, Resilient, Elastic and Message Driven. They have the appeal to be decoupled, scalable and handle error gracefully.
Responsiveness is the ability to rapidly and predictably respond. Resilient systems remain responsive even in the face of a failure. Recovery is possible without compromising the entire system – just like the human body can heal itself. Elastic systems can scale resource usage up or down depending on the workload given to the system.
Asynchronous message passing defines Reactive Systems as Message Driven. Loose coupling, isolation and location transparency is achieved with these messages.
Read more about the Reactive Manifesto on https://www.reactivemanifesto.org.
MDB – message driven beans and jms drives this cool nice topic mic.