JSP页面跳转显示数据问题!弄了几天了!求解决
<struts>
  <package name="mintao" extends="struts-default">
   <action name="zw" class="stuaction">
    <result type="redirectAction">getall</result>
    <result name="input">addstu.jsp</result>
   </action>
   <action name="getall" class="stuaction" method="getall">
     <result>showlist.jsp</result>
     <result name="input">addstu.jsp</result>
   </action>
   <action name="delstu" class="stuaction" method="delStudent">
     <result type="redirectAction">getall</result>
     <result name="input">detail.jsp</result>
   </action>
   <action name="updatestu" class="stuaction" method="updateStu">
     <result type="redirectAction">getall</result>
     <result name="input">detail.jsp</result>
   </action>
   <action name="getstu" class="stuaction" method="getStuById">
     <result>detail.jsp</result>
     <result name="input">showlist.jsp</result>
   </action>
  </package>
</struts>
//这个是showlist.jsp
<body>
     <form action="updatestu.action?id=${sid}" method="post">
        <table>
         <tr>
          <td>编号</td>
          <td>姓名</td>
          <td>年龄</td>
          <td>住址</td>
          <td>联系电话</td>
          <td>所在学校</td>
          <td>操作</td>
         </tr>          
         <!-- iterator 迭代  循环显示 -->          
         <s:iterator var="stu" value="stulist" >
          <tr>
          <td><s:property value="sid"/></td>
          <td><s:property value="sname"/></td>
          <td><s:property value="sage"/></td>
          <td><s:property value="sadress"/></td>
          <td><s:property value="sphone"/></td>
          <td><s:property value="school"/></td>           
          <!-- 当点击详细的时候,就是进行查询单个的操作,根据传的id查询对应的单个 -->           
          <td><input type="button" value="详细"  onclick="javascript:location.href='getstu.action?id=${sid}'"/></td>
         </tr>
         </s:iterator>
        </table>
     </form>
   </body>
</html>
//这个是detail.jsp
<body>
        <form action="">      
          <table>        
            <tr>
              <td>姓名:</td>
              <td><input type="text" value="${stu.sname }"></input></td>
            </tr>  
             <tr>
              <td>年龄:</td>
              <td><input type="text" value="${stu.sage }"></input></td>
            </tr