Controllers are the integration point between the model and resources in an Application. They act like the glue that binds everything together while taking care of business logic execution and response. 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>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-tomcat</artifactId>
   </dependency>
</dependencies>

The preceding dependency will import Asynchronous Servlets, Spring, and Tomcat dependencies to enable the successful writing of reactive web applications using Spring.