Question

我正在尝试以与此处相同的方式进行csv下载： How to provide a file download from a JSF backing bean?

我的回复一直在nullPointerException行投放output.write()。 bean是请求范围。关于空指针的任何想法？

    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

这里有3件事情跳出来

无法在responseComplete()上调用FacesContext，这意味着JSF将继续处理请求，并且不会影响结果。
reset()电话是不必要的。

输出流应为ServletOutputStream

类型

请尝试使用以下代码段

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，您只需致电sos.println(s)，无需在那里完成所有工作

bean中的JSF CSV下载

1 个答案: