Controllers are the integration point between the model and resources in a RESTful web service. They act like the glue that binds everything together while taking care of business logic execution and responses. The following Maven starter dependency needs to be added to enable Spring WebFlux:

<dependencies>
   ...
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-webflux</artifactId>
   </dependency>
</dependencies>

The preceding dependency will import the Reactive Stream, Spring, and Netty dependencies to enable the successful writing of Reactive web applications using Spring.