java.lang.IllegalStateException: getOutputStream() 已经为此响应调用

Here is my code for which I am getting the following exception

HTTP Status 500 - Unable to show problem report: java.lang.IllegalStateException: getOutputStream() has already been called for this response

代码:

WorkbookSettings wbSettings = new WorkbookSettings();    
OutputStream outStream = null;
            
try
{               
  wbSettings.setLocale(new Locale("en", "EN"));             
  response.setContentType("application/vnd.ms-excel");                  
  outStream= response.getOutputStream();                
  response.setHeader("Content-Disposition", "attachment; filename=/timesheet.xls");             
  WritableWorkbook workbook = Workbook.createWorkbook(outStream, wbSettings);              
  workbook.createSheet("Report", 0);               
  WritableSheet excelSheet = workbook.getSheet(0);              
  service.createLabel(excelSheet);              
  service.createContent(excelSheet);                    
  workbook.write();             
  workbook.close();             
  outStream.flush();               
  outStream.close();                
}               
catch(Exception e)
{
}           
finally
{               
  //outStream.close();      
}   
return "generateReport";

我的 Struts.xml 看起来像这样:

<result type="stream" name="generateReport">                   
 <param name="contentType">"application/vnd.ms-excel"</param>                  
 <param name="inputName">excelstream</param>                  
 <param name="contentDisposition">contentDisposition</param>                   
 <param name="bufferSize">1024</param>              
</result>