Struts2 问题 -include标签

A.jsp页面<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%@ taglib uri="/struts-tags" prefix="s"%><html>
  <head>  </head>
  
  <body>
    <s:include value="b.jsp" >
   <s:param name="msg">mymsgmymsg</s:param>
   </s:include>
  </body>
</html>
B.jsp页面<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%@ taglib uri="/struts-tags" prefix="s"%><html>
  <head>  </head>
  
  <body>
    1:<s:property value="#request.msg"/><br/>
    <%out.println("2:"+request.getParameter("msg")); %>
    
    <s:debug></s:debug>
    
  </body>
</html>为什么使用Include的时候 ， out.print可以取到 msg 而用ognl表达式却始终取不到