Firstly, may I assert that this is a perfectly reasonable question given the importance of CMS web technologies, which run a large portion of the WWW, and one rightly asked by many Java-aware people, as there are some serious problems with all of the many (nevertheless popular) PHP-based systems like Drupal, Wordpress, and Joomla, including:
inability to integrate well with graphical Unified Modeling Language (UML) engineering
massive use of freestyle strings as hash array keys (instead of as system-wide, shared, pre-defined string constants) in their programming style, burying data structure as hard-to-document conventions in hashmaps, and breaking everywhere the fundamental Don't Repeat Yourself (DRY) principle, instead of using reusable encapsulation with object-orientation
consequently poorer integration with IDEs and IDE prompting than a Java CMS API would permit.
There is a very good list of Java CMSs at:
http://en.wikipedia.org/wiki/List_of_content_management_systems#Java
The dotCMS site compares its own popularity with its main Java CMS competitors: Magnolia, Hippo, Jahia.
http://www.dotcms.com/images/carousel/banner/graph.png
It is interesting that OpenCMS does not make that list: http://www.opencms.org/
There is a CMS comparison tool at: http://www.cmsmatrix.org/
CMSmatrix lets you easily compare the features in over 1200 content
management system products.
The fact that there are 1200 indicates that asking others for tips or feedback on their experience with Java CMS variations is fair, as it is hard to test out all of the options.
As far as I can tell, dotCMS is the fastest growing and best option depending on your requirements.
Finally, permit me in my answer to offer an observation on the PHP vs Java CMS matter. My main language is Java, always, at least to some extent, under graphical UML model-driven engineering (if only sometimes via reverse engineering monitoring), but I have worked extensively with PHP and PHP-driven Drupal for many years, one of the "big three" along with Joomla and Wordpress.
As far as I can tell, none of the Java CMS options comes even close to the feature set of Drupal, when the massive range of contributed modules is considered, or (once you are familiar with it) the ease of setting up easy or very complex enterprise CMS sites with Drupal. In particular, the Views module in combination with ease of creation of custom content types makes it very easy to create very rich page displays with structured data, relationships, and rich query view reports. I do not know of any Java CMS that has anything that can even come close to matching the Drupal Views admin interface for creating custom query view reports. I am thankful that Drupal exists, and at times it has helped me to feed myself and my child, and I even use it to track my Enterprise Java software development projects, and I use it ironically for educational web sites promoting Unified Modeling Language (UML) and UML-driven Java.
Also, the CMS aspects of my own Java web applications deliberately imitate Drupal.
I make however no secret of the fact that I absolutely can't stand the basic Drupal programming model, the contributed module APIs, and what I consider to be an appalling lack of object-orientation in it, and a programming style that includes nearly every single sin I would as an educator discourage in any 101 programming course. I do not enjoy coding contributed modules against its API, and the Drupal hook system is completely unnecessary, and has no advantages over simple interface registration patterns that any Java programmer would know, and would let an OO compiler do.
I bemoan every working day the lack of a well-architected Java-based CMS that can otherwise match Drupal (while always remaining thankful for what one can do with Drupal).
With hot reload technologies for Java like JRebel, it should now be possible to have a Java-based CMS that is as easy to develop against as the PHP-driven CMSs but with a decent and properly object-oriented API, and I hope that one Java CMS does finally really take off and develop as active a contributed module community as the PHP-based ones like Drupal have.
