In the examples webapp all the struts-config.xml file use the "jakarta.apache.org/struts/dtds" url - Struts has moved to a TLP and these should now reference "struts.apache.org/dtds" (this is v.minor because "jakarta.apache.org/struts/dtds" is re-directing to "struts.apache.org/dtds").
The above is is also true for the tiles DTD definitions.
A number of the struts-config.xml have a Validator PlugIn defined - but only "app5" uses Commons Validator.
The validation.xml is referencing an old version of the Commons Validator DTD (v1.0 rather than v.1.1.3) and uses the deprecated "arg0" element.
Attaching a patch to correct all of the above