I have an existing JSP website which I would like to painlessly add CMS functionality to.

The site is a intranet portal and is backed by a database etc. however some pages like News and Events etc. I would like the user to be able to edit using a simple CMS. I would also like the user to be be able to create new pages and put them into the navigation system, like joomla does for PHP websites.

At the backend i am using mtsql database.

Now I could clearly code my own simple CMS but not wanting to reinvent the wheel is there any existing CMS that can be added to existing site and take advantage of the Master Pages model that I already have.

EDIT I have looked at Joomla, dotCMS, Jahia but as far as I can tell these can't be easily retro fitted. I also want to avoid (if possible) writing my own system using the FCK editor.

Thanks in advance