Book Image

Hands-On Reactive Programming with Reactor

By : Rahul Sharma
Book Image

Hands-On Reactive Programming with Reactor

By: Rahul Sharma

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)

Testing Reactor pipelines

Unit testing Reactor pipelines is quite hard. This is because Reactor declares behaviors rather than states that can be validated. Fortunately, Reactor comes with utility classes that can assist in unit testing. The testing utilities are bundled in the reactor-test component. reactor-test provides us with the following three components:

  • StepVerifier: Allows us to validate a pipeline configuration and operators
  • TestPublisher: Allows us to produce test data to enable testing operators
  • PublisherProbe: Enables us to validate an existing publisher

Before we proceed, let's first add reactor-test to our build.gradle. We do not need to specify the version of this as that is defined by the org.springframework.boot plugin:

plugins {
id "io.spring.dependency-management" version "1.0.1.RELEASE"
id "org.springframework.boot&quot...