I want to implement atmosphere for websocket and fallback mechanisms. But in the latest version of jhipster the support of Atmosphere has been removed. There is only support for spring websockets now. What steps should I take to move from spring websockets to atmosphere?
Originally there were some troubles when integrating atmosphere to spring. That led JHipster project to drop atmosphere support. AFAIK the last issue was in spring-boot and since it's fixed Atmosphere should play nicely with Spring. Unfortunately JHipster project did not re-add Atmosphere support so you will have to integrate the framework yourself.
I think you can take a look at this application that shows how to enable Atmosphere in spring-boot. The configuration is done in Java Config here.
If you want to use DI inside your Atmosphere services you might be interested by this page.