ZK Spring 3.1 is a maintenance release mainly focusing on fixing bugs and upgrading compatibility to fully support ZK 6. GenericSpringComposer has also been deprecated for better usage.
For details, please visit
http://blog.zkoss.org/index.php/2012/03/08/zk-spring-3-1-release-introduction/
or download it right away! http://www.zkoss.org/download/zkspring