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

Error recovery operators

Exceptions can occur in your Observable chain across many operators depending on what you are doing. We already know about the onError() event that is communicated down the Observable chain to the Observer. After that, the subscription terminates and no more emissions will occur. But sometimes, we want to intercept exceptions before they get to the Observer and attempt some form of recovery. We cannot necessarily pretend that the error never happened and expect emissions to resume, but we can attempt re-subscribing or switch to an alternate source Observable.

We can still do the former, just not with RxJava operators, which we will see shortly. If you find that the error recovery operators do not meet your needs, chances are you can compose them creatively.


For these examples, let's divide each integer emission by 10, where one of the emissions is 0. This will result in a "/ by zero" exception being emitted to the Observer, as shown in the following code snippet...