Have at least a local copy of built redis, for more information see [tutorial](https://www.digitalocean.com/community/tutorials/how-to-install-and-use-redis).
Prior to the build, you may need to change branch depending on which version of Redisson you want to build. Currently master branch is for version 2.x whereas 3.0.0 branch is for 3.x branch. Version 2.x requies Java SDK 6 and above and version 3.x requires Java SDK 8 and above to build.