Different Netty versions and their purposes

Question

I am using Netty for a while now and could never solve this question. One can download four different versions. Three of them are actively getting developed.

3.x

4.0.x

4.1.x

5.x

As far as I understand 3.x is for JRE 1.5 and everything else for JREs greater than that. I am using 4.0.28 because it is the stable and recommended version. But what exactly is the difference or goal of the other versions?

I could not find any information about this on their website.

EDIT: I see close votes coming so I'd like to clarify: I'm not looking for someone who lists me all the differences in the code of the versions. But there has to be some sort of objective or purpose for the 4.1.x and 5.x versions.

Answer 1

3.x is deprecated. We maintain it because some users still use it widely.

4.0 is the current stable version. When in doubt, use this version.

4.1 is a backward compatible version of 4.0. It adds some cool new features like HTTP/2 and asynchronous DNS resolver. So, 4.1 is the version you might want to try when your application already runs on top of 4.0 and you wanna try the new features.

5.0 is a backward incompatible version. However, it's not like a rewrite we did for 4.0 vs 3.x. However, we did fix some API design flaws. You'll need to make some changes in your code to make your Netty 4 application run on Netty 5, but it's not like porting Netty 3 application to Netty 4 application. Eventually, 4.x will be deprecated and 5.0 will be a stable version.

Answer 2

It should be noticed that 5.0 had been revoked in Nov 2015, 4.1 is the newest stable version now.

Answer 3

If you want to know what are all new (and noteworthy changes) between these versions, you can visit these links:

3.x -> 4.0

4.0 -> 4.1

4.x -> 5.0