To be on the same page needs to make Ajax call, as far as you using struts2-jquery plugin it's easy done via
place it on the JSP
<%@ taglib prefix="sj" uri="/struts-jquery-tags" %>
<head>
<sj:head/>
</head>
<s:div id="result"/>
<s:form action="product" method="POST"/>
<sj:submit method="loadsearch" id="find" targets="result" />
</s:form>