What is the difference between ProjectReactor.io vs Spring WebFlux?

Question

What is the difference between ProjectReactor.io vs Spring WebFlux?

I've read the documentation here: https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html and https://projectreactor.io/, for me both are very similar to each other. I am interested to learn the highlights on this.

Answer 1

They are on different abstraction level, so they can't really be compared as such.

Project Reactor is a general purpose reactive library. Similarly to RxJava, it is based on the reactive-streams specification. It is like Java 8 Stream and Optional, except it has support for asynchronous programming, error handling is built-in, supports backpressure and has a large number of operators (map, filter and many more).

Spring Webflux is a framework to create web services using reactive libraries. Its main goal is to ensure high scalability with low resource usage (i.e. small number of threads). Under the hood it uses Project Reactor, however, you can also use it with RxJava (or any other reactive-streams implementation) and it works well even with Kotlin Coroutines.