Save file as - dialog box with dynamic data

Question

I know that this question is quite common, but its specifics are stumping me.

I have an "export" button which I want to take a load of data generated, create a CSV file, then pop up a Save File As dialog box, to save that file on their local machine.

The name of this file is dynamic, also.

I know how to make the CSV file, but how do I then pop up a box on the client side to let the user download it?

I am using JSP with Struts

Answer 1

All you need to do is to send a response containing your generated csv with a header:

Content-Disposition: attachment; filename=your_file.csv

Answer 2

Thanks to Max for his answer, but after getting further with this I am hitting a new problem. I am setting the header of the response, then creating a ServletOutputStream to pass my data to. The problem I am having, is that I am getting an error

getOutputStream() has already been called for this response

I have found that the reason for this, is that my Action class is returning an ActionForward and this will attempt to write more data to the output stream.

Is there a way of getting around this without removing the return type, because this is needed elsewhere.