Integration of Sharepoint and Java seems to be a tough thing to do. Having a look on the web there is not much info about it besides these posts about Sharepoint and Java.
http://derekjmiller.spaces.live.com/blog/cns!A77124B9D0EE317F!142.entry
http://derekjmiller.spaces.live.com/blog/cns!A77124B9D0EE317F!167.entry
http://knowledgeforward.wordpress.com/2007/07/31/integration-with-sharepoint-and-anything/
Having a look at the issue, probably it's because of Java's ABM stance - lousy SOAP support, as it needs AXIS libraries and poor tools support for Web Services (unlike Visual Studio which autogenerates code stubs out of ANY WSDL/SOAP almost by default be it Java or else).