In the previous sections, we learned how to use pure RxJava and how to combine it with Spring Web MVC. To demonstrate the benefits of this, we have updated our temperature-monitoring application and improved the design by applying RxJava. However, it is worth noting that Spring Framework and RxJava is not the only valid combination. A lot of application servers also value the power of the reactive approach. As such authors of a successful reactive server called Ratpack decided to adopt RxJava as well.
Along with callbacks and a promise-based API, Ratpack provides RxRatpack, a separate module that allows to convert Ratpack Promise to RxJava Observable easily, and vice versa, as shown in the following code:
Promise<String> promise = get(() -> "hello world");
RxRatpack
.observe(promise)
.map(String::toUpperCase)
.subscribe...