How to open popup window for "preview html"

[A Bhattacharya]

protected ModelAndView onSubmit(HttpServletRequest request,
			HttpServletResponse response, Object command, BindException errors)
			throws Exception 
{
. . . 
response.setContentType("text/html");
response.setHeader("Content-Disposition", "attachment; filename="
					+ fileName);
OutputStream outputStream = response.getOutputStream();
outputStream.write(bodyTxt.getBytes());
outputStream.flush();

I have the above code that pushes a html attachment to response stream. This results in the browser asking whether to open or save the file, and if we choose open, it opens in the same window and thus the form disappears. How to make it open in a pop up window or new tab so that the form is intact?