Struts2中怎样配置struts。xml？

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.1//EN"
"http://struts.apache.org/dtds/struts-2.1.dtd">
<struts>
<constant name="struts.i18n.encoding" value="utf-8"/>
<constant name="struts.ui.theme" value="simple"/>
<constant name="struts.custom.i18n.resources" value="application"></constant>
<package name="default" extends="struts-default" namespace="/">
<action name="struts" class="org.struts.StrutsAction">
<result name="success">/welcome.jsp</result>
<result name="error">/error.jsp</result>
</action>
</package>
</struts>