Reactive Programming with RxJava

Chapter 4. Applying Reactive Programming to Existing Applications

Tomasz Nurkiewicz

Introducing a new library, technology, or paradigm to an application, be it greenfield or legacy codebase, must be a careful decision. RxJava is not an exception. In this chapter, we review some patterns and architectures found in ordinary Java applications and see how Rx can help. This process is not straightforward and requires a significant mindset shift, therefore we will carefully transform from imperative to functional and reactive style. Many libraries in Java projects these days simply add bloat without giving anything in return. However, you will see how RxJava not only simplifies traditional projects, but what kinds of benefits it brings to legacy platforms.

I am pretty sure that you’re already very excited about RxJava. Built-in operators and simplicity makes Rx an amazingly powerful tool for transforming streams of events. However, if you go back to your office tomorrow, you will realize that there are no streams, no real-time events from stock exchange. You can hardly find any events in your applications; it’s just a mash-up of web requests, databases, and external APIs. You are so eager to try this new RxJava-thing somewhere beyond Hello world. Yet it seems that there are simply no use cases in real life that justify using Rx. Yet, RxJava can be a significant step forward in terms of architectural consistency and robustness. You do not need to commit to reactive style top-to-bottom—this ...