Book Image

Hands-On Reactive Programming with Reactor

Book Image

Hands-On Reactive Programming with Reactor

Overview of this book

Reactor is an implementation of the Java 9 Reactive Streams specification, an API for asynchronous data processing. This specification is based on a reactive programming paradigm, enabling developers to build enterprise-grade, robust applications with reduced complexity and in less time. Hands-On Reactive Programming with Reactor shows you how Reactor works, as well as how to use it to develop reactive applications in Java. The book begins with the fundamentals of Reactor and the role it plays in building effective applications. You will learn how to build fully non-blocking applications and will later be guided by the Publisher and Subscriber APIs. You will gain an understanding how to use two reactive composable APIs, Flux and Mono, which are used extensively to implement Reactive Extensions. All of these components are combined using various operations to build a complete solution. In addition to this, you will get to grips with the Flow API and understand backpressure in order to control overruns. You will also study the use of Spring WebFlux, an extension of the Reactor framework for building microservices. By the end of the book, you will have gained enough confidence to build reactive and scalable microservices.
Table of Contents (13 chapters)

WebClient

In Chapter 6, Dynamic Rendering, we discussed using the Spring WebClient to make web calls in a non-blocking and asynchronous manner. The operators that we have discussed so far are applicable to Reactive Stream publishers and subscribers. WebClient also produces a Mono publisher of ServerResponse. So, how should we handle errors generated in WebClient, and generate a valid response? First, let's take a look at WebClient's default handling of server-side errors. To do this, we should first generate errors in our Fibonacci handler function, as follows:

   @Bean
RouterFunction<ServerResponse> fibonacciEndpoint() {
Flux<Long> fibonacciGenerator = Flux.generate(() -> Tuples.<Long,
Long>of(0L, 1L), (state, sink) -> {
throw new RuntimeException("Method unsupported");
});
RouterFunction...