tomcat启动警告：Could not parse struts.locale setting, substituting default VM locale,该如何处理

tomcat启动警告：Could not parse struts.locale setting, substituting default VM locale
<?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>
<constant name="struts.locale" value="en_US"/>

<package name="struts2test" extends="struts-default">
<action name="test" class="com.Test">
<result name="success">index1.jsp</result>
<result name="error">index2.jsp</result>
</action>
</package>
</struts>
以上是我的struts.xml为什么添加了<constant name="struts.locale" value="en_US"/>
还有同样的警告啊？用这个<constant name="struts.locale" value="en_GB" /> 我也试过了，警告依旧

------解决方案--------------------
估计没解