Apache Jackrabbit is an open source content repository for Java. It is fully compliant to JSR 170 specification,
I am an ardent fan of this utility.
If you are really looking at a small scale implementation of a Document/content Management system like say something to cater to specific regulatory compliances etc , then Jackrabbit is for you.
Jackrabbit can be used for the back-end document management system. The Jackrabbit Library services should be utilized for rendering the DM services. It does provide search and retrieval, version control and email services to name a few. Anything that is not available could be built as a simple webservice. The UI needs can be customised with any home grown system. The good part is it can well be integrated with search engines like Lucene, another Open source option.
Talk about open source exploitation !
