I'm looking for a CMS (content management system), where users can manage, create and edit online articles, as a part of an application to be developed. The application to develop is a web application running on Tomcat, with a PostgreSQL connection and using the Spring web framework. I'm looking for a CMS, which can be seamlessly integrated into our own application, without the user noticing where the CMS ends and our application starts, and vice versa.
So far I've seen that OpenCMS (http://www.opencms.org/en/index.html) looks like a good candidate, as you can display content with a custom tag library. There is also a good list of options on Wikipedia page at http://en.wikipedia.org/wiki/List_of_content_management_systems
I would like to hear personal experiences and recommendations for a CMS integrated with a Java-based web application.