WebWork 2.2.1 is a bugfix release for the 2.2 release a month ago.
If you have used the previous portlet integration code, you should check the portlet-webapp for an example.
The DTD public IDs in xwork.dtd were incorrect in the 1.1. release.
Make sure your DOCTYPE definitions for xwork.xml files look like this:
For xwork 1.1:
<!DOCTYPE xwork PUBLIC
"-//OpenSymphony Group//XWork 1.1//EN""http://www.opensymphony.com/xwork/xwork-1.1.dtd">
For xwork 1.1.1:
<!DOCTYPE xwork PUBLIC
"-//OpenSymphony Group//XWork 1.1.1//EN""http://www.opensymphony.com/xwork/xwork-1.1.1.dtd">
Changelog
For a complete list of all the changes, please refer to the complete changelog