Book Image

Learning RxJava

By : Thomas Nield
Book Image

Learning RxJava

By: Thomas Nield

Overview of this book

RxJava is a library for composing asynchronous and event-based programs using Observable sequences for the JVM, allowing developers to build robust applications in less time. Learning RxJava addresses all the fundamentals of reactive programming to help readers write reactive code, as well as teach them an effective approach to designing and implementing reactive libraries and applications. Starting with a brief introduction to reactive programming concepts, there is an overview of Observables and Observers, the core components of RxJava, and how to combine different streams of data and events together. You will also learn simpler ways to achieve concurrency and remain highly performant, with no need for synchronization. Later on, we will leverage backpressure and other strategies to cope with rapidly-producing sources to prevent bottlenecks in your application. After covering custom operators, testing, and debugging, the book dives into hands-on examples using RxJava on Android as well as Kotlin.
Table of Contents (21 chapters)
Title Page
About the Author
About the Reviewers
Customer Feedback

A brief history of ReactiveX and RxJava

As developers, we tend to train ourselves to think in counter-intuitive ways. Modeling our world with code has never been short of challenges. It was not long ago that object-oriented programming was seen as the silver bullet to solve this problem. Making blueprints of what we interact with in real life was a revolutionary idea, and this core concept of classes and objects still impacts how we code today. However, business and user demands continued to grow in complexity. As 2010 approached, it became clear that object-oriented programming only solved part of the problem. Classes and objects do a great job of representing an entity with properties and methods, but they become messy when they need to interact with each other in increasingly complex (and often unplanned) ways. Decoupling patterns and paradigms emerged, but this yielded an unwanted side effect of growing amounts of boilerplate code. In response to these problems, functional programming began to make a comeback, not to replace object-oriented programming, but rather to complement it and fill this void. Reactive programming, a functional event-driven programming approach, began to receive special attention. A couple of reactive frameworks emerged ultimately, including Akka and Sodium. But at Microsoft, a computer scientist named Erik Meijer created a reactive programming framework for .NET called Reactive Extensions. In a matter of years, Reactive Extensions (also called ReactiveX or Rx) was ported to several languages and platforms, including JavaScript, Python, C++, Swift, and Java, of course. ReactiveX quickly emerged as a cross-language standard to bring reactive programming into the industry. RxJava, the ReactiveX port for Java, was created in large part by Ben Christensen from Netflix and David Karnok. RxJava 1.0 was released in November 2014, followed by RxJava 2.0 in November 2016. RxJava is the backbone to other ReactiveX JVM ports, such as RxScala, RxKotlin, and RxGroovy. It has become a core technology for Android development and has also found its way into Java backend development. Many RxJavaadapter libraries, such as RxAndroid (, RxJava-JDBC (, RxNetty (, and  RxJavaFX ( adapted several Java frameworks to become reactive and work with RxJava out of the box. This all shows that RxJava is more than a library. It is part of a greater ReactiveX ecosystem that represents an entire approach to programming. The fundamental idea of ReactiveX is that events are data and data are events. This is a powerful concept that we will explore later in this chapter, but first, let's step back and look at the world through the reactive lens.