DocBook Java Tools
There are a variety of tools for using DocBook XSL in a cross-platform Java environment. I'm personally interested in Open Source Tools based upon Apache Ant and Apache Maven. This page currently attempts to catalog some of the available options, but I still haven't found the ideal solution. I've created some tools I call DocBook Suite and packaged them as a Maven 1.x plug-in called maven-dbsuite-plugin.
The maven-dbsuite-plugin is a tool that I created to meet (most of) my requirements for DocBook processing. It is useful to me in its current form and may be useful to others, so I have created a project for it on Java.net.
These Ant tasks can be used to do DocBook processing using the Ant build tool. They also are the building blocks for maven-dbsuite-plugin, and the other Maven plug-ins listed below.
There have been several other Maven plug-ins for DocBook, but only one the SourceForge project is still active. (Although the last change appears to have been made in January, 2005.)