As we saw in Chapter 1, Why Reactive Spring?, and Chapter 4, Project Reactor - the Foundation for Reactive Apps, the new era of application servers has brought new techniques for developers. From the beginning of Spring Framework's evolution in the field of web applications, the decision was made to integrate the Spring Web module with Java EE's Servlet API. The entire infrastructure of the Spring Framework is built around Servlet API and they are tightly coupled. For instance, the entirety of Spring Web MVC is based on the Front Controller pattern. That pattern is implemented in Spring Web MVC by the org.springframework.web.servlet.DispatcherServlet class, which indirectly extends the javax.servlet.http.HttpServlet class.

On the other hand, the Spring Framework does give us a better level...