Using Open CSV to Send files from ServletOutputStream

Question

I have parsed a JSON Object that was sent to my TOMCAT server using POST and turned it into a CSV file. I would like to send the CSV file back to the user. I am confused about how to send the file back because all the examples I have seen reference an actual file that is stored on the server - my file is built in memory and doesn't actually reference a file/file descriptor as far as I can tell.

//The doPost method has already generated the String[] - I then call generateCSV


protected void generateCSV(ArrayList<String[]> data, ServletOutputStream out,
                           HttpServletResponse response)
{
    try{
        BufferedWriter buff = new BufferedWriter(new OutputStreamWriter(out));
        CSVWriter writer = new CSVWriter(buff);
            writer.writeAll(data);
            writer.close();

        sendFile(response, out);

    }catch(IOException | ServletException e){

        e.printStackTrace();
    }


}


protected void sendFile(HttpServletResponse response, ServletOutputStream outstream)throws ServletException, IOException
{
    response.setContentType("application/octet-stream");
    outstream.flush();
    outstream.close();
}

Answer 1

What do you have to do to send a file to the user from a servlet?

1. Set the content-type.
2. Write out the bytes.

Seems to me you are doing this, but in the wrong order. Also, rather than using application/octet-stream you might want to actually tell the browser this is CSV. You might also want to give it a filename.

    response.setContentType("text/csv");
    response.setHeader("Content-Disposition","filename=whatever.csv");
    BufferedWriter buff = new BufferedWriter(new OutputStreamWriter(out));
    CSVWriter writer = new CSVWriter(buff);
        writer.writeAll(data);
        writer.close();