You will learn how to integrate RESTful Java microservices with a reactive system by using MicroProfile Reactive Messaging. RESTful Java microservices don’t use reactive concepts, so you will learn how to bridge the gap between the two using the RxJava library. In this guide, you will modify two microservices in an application so that when a user hits the RESTful endpoint, the microservice generates producer events.

The application in this guide consists of two microservices, system and inventory. The following diagram illustrates the application:
Every 15 seconds, the system microservice calculates and publishes events that contain its current average system load. The inventory microservice subscribes to that information so that it can keep an updated list of all the systems and their current system loads. The current inventory of systems can be accessed via the /systems REST endpoint.

You will update the inventory microservice to subscribe to a PUT request response. This PUT request response accepts a specific system property in the request body, queries that system property on the system microservice, and provides the response. You will also update the system microservice to handle receiving and sending events that are produced by the new endpoint. You will configure new channels to handle the events that are sent and received by the new endpoint. To learn more about how the reactive Java services that are used in this guide work, check out the Creating reactive Java microservices guide.

The Open Liberty Project team