java.lang.ClassCastException: java.io.FileInputStream cannot be cast to java.lan

做Extjs+Struts2文件上传、下载，做下载功能的时候一直爆[color=red]java.lang.ClassCastException: java.io.FileInputStream cannot be cast to java.lang.String[/color]这个错误，找了好久，发现原来是Struts2配置文件出错，

原代码如下:

<action name="downMachErrorDataAction"  class="cn.org.genomics.health.solexaHlaPl.tongchou.action.DownMachErrorDataAction" method="getInputStream">
     
   <result name="success" type="stream">
    <param name="contentType">application/vnd.ms-excel</param>
    <param name="contentDisposition">
     attachment;filename =
     "${fileName}"
    </param>
       </result>
  </action>

修改成以下代码就OK了

 <action name="downMachErrorDataAction"  class="cn.org.genomics.health.solexaHlaPl.tongchou.action.DownMachErrorDataAction">
   <result name="success" type="stream">
    <param name="contentType">application/vnd.ms-excel</param>
    <param name="contentDisposition">
     attachment;filename =
     "${fileName}"
    </param>
    <param name="inputName">inputStream</param><!--action的方法名-->
   </result>
  </action>