extensions/struts2/src/struts-plugin.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE struts PUBLIC
  "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
  "http://struts.apache.org/dtds/struts-2.0.dtd">
    
<struts>

  <bean type="com.opensymphony.xwork2.ObjectFactory" 
        name="guice"
        class="com.google.inject.struts2.Struts2Factory"/>

  <!--  Make the Guice object factory the automatic default -->
  <constant name="struts.objectFactory" value="guice" />

</struts>