We have been using the internet for more than a decade now. Today, the entire world is online, and each one of us is using it for our day-to-day requirements. Although Internet has been with us since a long time, in the early days, its use was limited. It was used to request for a resource and get a response in turn that, most of the time, was an HTML page or image to download. However, today, the look and feel, the requirements, the use, the data formats, the expectations of the user and, more importantly, the mechanism have changed a lot. Internet is handling a tremendous load of data, and it's obviously hampering their performance. The request and response, as we all know, is synchronous. The user needs to wait for the response. It addresses a major problematic area--blocking of streams--that keeps the users waiting, and they never know how long they have to keep waiting. The solution to this problem is a quick response without blocking. We are talking about today's hot topic--the Reactive Streams.

In this chapter, we will discuss non-reactive streams with the help of the following points:

• What is reactive programming?
• The basics of reactive programming
• Spring support for reactive programming
• Developing a web application using reactive programming