Two weeks ago I blogged about integration of Spring and Sling into Spling (btw: if you speak German check out Sandro Ruch's post on the topic). Regarding access to the repository content from a Spring-based application I wrote back then:
So integrating the content really just involves sending HTTP requests. This approach will carry you very far without having to resort to JCR connections (but it surely feels comforting that this lower level access is always there).
Of course, in the workshop described in the post we were considering only Communique 5 which is built on top of Sling. However, in Communique 4 there is no Sling so it is more likely that you end up in a situation were you want to access the repository through JCR.