Vert.x in Action

5 Beyond callbacks

This chapter covers

• Callbacks and their limitations, as shown with a gateway/edge service example
• Futures and promises--a simple model to chain asynchronous operations
• Reactive extensions--a more powerful model that is especially well suited to composing streams of asynchronous events
• Kotlin coroutines--language-level support for asynchronous code execution flows

You will need to write all sorts of business logic while developing a reactive application, and not all logic is easy to express in an asynchronous form. While callbacks are a simple form of asynchronous event notification, they can easily render asynchronous code complicated.

Let’s look at a real example of why callbacks are not always the best asynchronous programming ...