JSF CSV在bean中下载

Question

我正在尝试以与此处相同的方式下载csv：如何提供从JSF支持bean下载的文件？

我的响应不断向output.write()行抛出nullPointerException。bean属于请求范围。对空指针有什么想法吗？

    try
    {
        //submitForm();
        FacesContext fc = FacesContext.getCurrentInstance();
        HttpServletResponse response = (HttpServletResponse) fc.getExternalContext().getResponse();
        response.reset();
        response.setContentType("text/csv"); 
        //response.setContentLength(contentLength); 
            response.setHeader ( "Content-disposition", "attachment; filename="Reporting-" + 
                    new Date().getTime() + ".csv"" );
        OutputStream output = response.getOutputStream();
        String s = ""Project #","Project Name","Product Feature(s)",";
        s+=""Project Status",";
        s+=""Install Type",";
        s+=""Beta Test","Beta Test New/Updated",";
        s+=""Production","Production New/Updated",";
        s+="n";
        InputStream is = new ByteArrayInputStream( s.getBytes("UTF-8") );
        int nextChar;
         while ((nextChar = is.read()) != -1) 
         {
            output.write(nextChar);
         }
         output.close();
    }
    catch ( IOException e )
    {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

Answer 1

3件事跳出这里

1. 如果不能在FacesContext上调用responseComplete()，那么JSF将继续处理请求，并且不会影响结果。

2. reset()调用是不必要的。

3. 输出流应为ServletOutputStream 类型

   尝试以下代码段而不是

   try
   {
   //submitForm();
   FacesContext fc = FacesContext.getCurrentInstance();
   HttpServletResponse response = (HttpServletResponse) fc.getExternalContext().getResponse();
   
   response.setContentType("text/csv"); 
   fc.responseComplete();
   //response.setContentLength(contentLength); 
       response.setHeader ( "Content-disposition", "attachment; filename="Reporting-" + 
               new Date().getTime() + ".csv"" );
   ServletOutputStream output = response.getOutputStream();
   String s = ""Project #","Project Name","Product Feature(s)",";
   s+=""Project Status",";
   s+=""Install Type",";
   s+=""Beta Test","Beta Test New/Updated",";
   s+=""Production","Production New/Updated",";
   s+="n";
   InputStream is = new ByteArrayInputStream( s.getBytes("UTF-8") );
   int nextChar;
    while ((nextChar = is.read()) != -1) 
    {
       output.write(nextChar);
    }
       output.flush();
    output.close();
   }
   catch ( IOException e )
   {
    // TODO Auto-generated catch block
       e.printStackTrace();
   }
   

此外，您可以直接调用sos.println(s)，而无需在那里进行所有工作