Struts Ajax 导出Excel

<package name="crankcall" extends="json-default" namespace="/crankcall">
  <!-- 下载导出excle -->
  <action name="exportExcel" class="....action.ExportExcelAction" method="download" >
   <result name="excel" type="stream"> 
       <!-- ISO8859-1 -->
       <param name="contentType">application/vnd.ms-excel,charset=UTF-8</param>
       <param name="contentDisposition">

                         attachment;filename="${fileName}.xlsx"

       </param> 
       <param name="bufferSize">4096</param>
       <param name="inputName">excelFile</param> 
   </result>
  </action>
 </package>

pubic InputStream excelFile; // 下载文件流

private String fileName; // 下载文件名称

public String download() throws Exception {

      /*

         使用POI来创建表格，datas为要导出的数据。

         WorkbookUtil为自定义的工具类

     * /
      XSSFWorkbook workbook =WorkbookUtil.createWorkBook(datas);
      if(workbook == null){
          log.info("导出数据失败");
           return ERROR ;
      }
      ByteArrayOutputStream output = new ByteArrayOutputStream();
      workbook.write(output);
      byte[] ba = output.toByteArray();
      excelFile = new ByteArrayInputStream(ba);
      output.flush();
      output.close();
      return "excel";
}

public String getFileName() {
      String timestamp = new SimpleDateFormat("yyyyMMddHHmmss").format(new Date()) ;
      fileName = fileName+timestamp ;
      try {
           fileName = new String(fileName.getBytes(),"ISO8859-1") ;
      } catch (UnsupportedEncodingException e) {
           fileName = timestamp ;
      }
      return fileName;
 }

function exportExcelByForm(fileName){
       var mform = document.getElementById(‘excel_export_form‘) ;
       if(mform){
             document.body.removeChild(mform) ;
       }
       mfrom = document.createElement("form");
       mfrom.id = "excel_export_form" ;
       mfrom.target="_blank" ;
       mfrom.method="post" ;
       mfrom.action="crankcall/export/exportExcel.action" ;
       mfrom.style.display="none" ;
 
       var fname = document.createElement("input");
       fname.type = "hidden";
       fname.name = "fileName";
       fname.value = fileName ;
       mfrom.appendChild(fname);

       //TODO 可以继续传递更多的参数或者数据到服务端
 
       document.body.appendChild(mfrom);
       mfrom.submit();
}