portlet/src/main/resources/struts-tiles.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
	"-//Apache Software Foundation//DTD Struts Configuration 2.5//EN"
	"https://struts.apache.org/dtds/struts-2.5.dtd">

<struts>
    <package name="tiles" extends="struts-portlet-tiles-default" namespace="/tiles">
        <default-action-ref name="index"/>

        <action name="index" class="org.apache.struts2.portlet.example.FormExample">
            <result type="tiles">formExampleTiles.index</result>
            <result name="success" type="tiles">formExampleTiles.index</result>
        </action>

        <action name="processTilesFreemarkerExample" class="org.apache.struts2.portlet.example.FormExample" method="input">
            <result name="success" type="tiles">formExampleTiles.freemarker</result>
        </action>

        <action name="processTilesFreemarkerExample" class="org.apache.struts2.portlet.example.FormExample" method="execute">
            <result name="input" type="tiles">formExampleTiles.freemarker</result>
            <result name="success" type="tiles">formExampleTiles.freemarkerResult</result>
        </action>

    </package>
</struts>