Modifying struts-config.xml File

Change the RequestProcessor to org.apache.struts.action.PortletRequestProcessor or org.apache.struts.tiles.PortletTilesRequestProcessor, if the application is using Tiles.

For example:

<controller 
contentType="text/html;charset=UTF-8"
debug="3"
locale="true"
processorClass="org.apahce.struts.action.PortletRequestProcessor">
<!-- The "input" parameter on "action" elements is the name of a
local or global "forward" rather than a module-relative path -->
<set-property property="inputForward" value="true"/>
</controller>