We will develop microservices that contain business logic based on plain Spring Beans and expose REST APIs using Spring WebFlux. The APIs will be documented based on the OpenAPI specification using springdoc-openapi. To make the data processed by the microservices persistent, we will use Spring Data to store data in both SQL and NoSQL databases.

Since Spring Boot v2.0 was released in March 2018, it has become much easier to develop reactive microservices, including non-blocking synchronous REST APIs. To develop message-based asynchronous services we will use Spring Cloud Stream. Refer to Chapter 1, Introduction to Microservices, the Reactive microservices section, for more information.

Finally, we will use Docker to run our microservices as containers. This will allow us to start and stop our microservice landscape, including database servers and a message broker, with a single command.

That's a lot of technologies and frameworks, so let's go through each of them briefly to see what they are about!

In this chapter, we will introduce the following open source projects:

Spring Boot

Spring WebFlux

springdoc-openapi

Spring Data

Spring Cloud Stream

Docker