I upgrade my application from 2.1.8 to 22.214.171.124, then find that <s:url> can't geneate proper result when I don't assign namespace value in the <s:url> tag. e.g, <s:url value="aaaa/">, in the old version, I got "http://xxx/xxxx&struts.portlet.action=/somenamespace/aaaa", but in the new version, I got "http://xxx/xxxx&struts.portlet.action=/aaaa", the namespace is missing.
I check source code between 2.1.8 and 126.96.36.199, and find in org.apache.struts2.components.PortletUrlRenderer
This statement is missing in 188.8.131.52, which cause struts can't find namespace by action name. I think it's losing feature.