java.lang.IllegalStateException : getOutputStream() has already been called for this response

Question

这是我的代码，我收到以下异常

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 如下所示:

<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>

在 JSP 中，我只是提供了一个按钮，它提供了打开、保存对话框。单击该按钮后，我收到异常。

如何避免这种情况？

Answer 1

这只是一个语法错误，服务器混淆了如何处理此类内容类型

<param name="contentType">"application/vnd.ms-excel"</param>

更改为

<param name="contentType">application/vnd.ms-excel</param>

注意，param 值是一个不带双引号的字符串。

因此，有效结果为

<result type="stream" name="generateReport">
  <param name="contentType">application/vnd.ms-excel</param>
  <param name="contentDisposition">attachment;filename="timesheet.xls"</param>
  <param name="inputName">excelstream</param>
</result>

操作代码应初始化 excelstream 并在返回结果之前提供 getter。 workbook 不应写入响应，而应将其写入 ByteArrayOutputStream。

private InputStream excelstream;

public InputStream getExcelstream() {
  return excelstream;
}  

public String execute() throws Exception {
  WorkbookSettings wbSettings = new WorkbookSettings();

  try  {  
    ByteArrayOutputStream outstream = new ByteArrayOutputStream();  
    wbSettings.setLocale(new Locale("en", "EN"));        
    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();  
    excelstream = new ByteArrayInputStream(outstream.toByteArray());        
  } catch(Exception e) {    
    e.printStackTrace();
    throw e;
  }

  return "generateReport";
}