I haven't used a real CMS but I liked Wikis so much I wrote one.
Google for "java conent management" maybe with "open source" thrown in and see what you find. I did a quick survey before deciding to write a Wiki and didn't find anything that met my needs. Your requirements may be different enough you'll find just what you need.
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi