Reactive Systems in Java

Introduction

The book «Reactive Systems in Java» (authors: Clement Escoffier and Ken Finnigan, 2021, 330 pages) is a practical guide to designing and developing modern reactive systems. Despite its name, the book actively uses the Kotlin language (alongside Java), making it especially valuable for developers working in the JVM ecosystem. The authors are recognized experts in reactive programming: Clement Escoffier is known for his contributions to the Vert.x project, and Ken Finnigan is the author of books on WildFly and JBoss.

The book was published in 2021, but its ideas and approaches remain relevant today, as the reactive paradigm continues to gain popularity in microservice architecture and cloud applications.

What the book is about

The book focuses on building reactive systems — distributed applications that respond quickly to requests, are resilient to failures, scale, and remain responsive even under high load. The authors systematically cover all aspects of the reactive approach, based on the Reactive Manifesto (responsiveness, resilience, elasticity, message-driven).

Special attention is given to the practical use of libraries and frameworks: Eclipse Vert.x (for building reactive microservices), Mutiny (a reactive library for Java/Kotlin), as well as integration with databases, message queues, and external services. Examples