Hi,
Since XML is an SGML variant that allows a free-form tag (that would be the field name of the database) and then builds from there. I suggest MySQL since it is also Sun as Java is. You did not specify a database. There is JDBC (Java DataBase Connector) that works with other databases, as well. For a discussion of this:
http://forums.mysql.com/read.php?39,20964
There is another solution. It is more elegant, though more more involved. It is the use of Linux or Windows with MySQL or PostgreSQL, and Drupal (which involves PHP for full functionality.) See:
drupal.org | Community plumbing
It is a beautiful system, open source, lots of templates and modules. Learning curve can be a bit much, but the demand for developers is amongst the highest in the world.
Peace,
Clarke