The new version of the HTTP protocol, HTTP/2 lets the server to push content to the client before the client requests the particular content. There are many other modifications in the protocol if we compare the previous version 1.1 with the new version 2, but, in this article, I will focus on the push functionality. I will discuss briefly how it can be used in a servlet, and I will also discuss a bit about how to test and see that it really works at all or not. Before writing this article my original intention was to create a demonstration of HTTP/2 showing how much faster the sample page load is with the push than it is without. It is going to be one chapter in my video tutorial that is published by PACKT. During the development of the sample application I faced several problems, I have read some tutorials and debugged the sample code a bit using what I gathered during this experience. In this article, I share this experience with you. That way this article is a bit more than just a simple introductory tutorial. Nevertheless, it is also a bit longer, so TLDR; if you are impatient.
HTTP/2 is a new version of the HTTP protocol. The protocol had three versions prior to 2. They were 0.9, 1.0, and 1.1. The first one was only an experiment starting in 1991. The first real version was 1.0 released in 1996. This was the version that you probably met if you were using the internet at that time and you still remember the Mosaic browser. This version was soon followed by version 1.1 in 1997. The major difference between 1.0 and 1.1 was the Host header field that made it possible to operate several websites on one machine, one server, one IP address, and one port.