JSF h:commandLink 提交后只刷新页面不执行绑定的后台方法

 <h:form> 
<h:commandButton value="查询" action="#{studao.query}"></h:commandButton>
</h:form>        
        <center>
         <h:form>
        <h:dataTable value="#{studao.slist}" var="s" border="1">
        <h:column>
         <f:facet name="header">
             <h:outputText value="学生编号"/>
         </f:facet>
            <h:outputText value="#{s.sid}"/>
        </h:column>
        <h:column>
         <f:facet name="header">
             <h:outputText value="学生名"/>
         </f:facet>
            <h:outputText value="#{s.sname}"/>
        </h:column>
        <h:column>
         <f:facet name="header">
             <h:outputText value="密码"/>
         </f:facet>
            <h:outputText value="#{s.pass}"/>
        </h:column>
         <h:column>
         <f:facet name="header">
             <h:outputText value="性别"/>
         </f:facet>
            <h:outputText value="#{s.sex}"/>
        </h:column>
        <h:column>
         <f:facet name="header">
             <h:outputText value="年龄"/>
         </f:facet>
            <h:outputText value="#{s.age}"/>
        </h:column>
       
        <h:column>
         <f:facet name="header">
             <h:outputText value="生日"/>
         </f:facet>
            <h:outputText value="#{s.birth}"/>
        </h:column>
        
        <h:column>
         <f:facet name="header">
             <h:outputText value="操作"/>
         </f:facet>
        
         <h:commandLink action="#{studao.del}">
         <h:outputText value="删除"></h:outputText>
         <f:param value="#{s.sid}" name="sid"></f:param>
         </h:commandLink>
        
        </h:column>
        
     </h:dataTable>
     </h:form>