How to get download csv file using java servlet?

You're writing to a file instead of to the HTTP response.

• You need to write the CSV to HttpServletResponse#getWriter().
• You need to set Content-Disposition header to attachment to force a Save As dialogue in the webbrowser, eventually along with a filename attribute. There's one (major?) caveat: the MSIE browser won't use the specified filename as actual file name in the Save As dialogue, it will instead use the last part of the pathinfo of the URL.
• You need to set Content-Type header to text/csv to instruct the webbrowser what kind of file it is so that it can find the correct associated application when the enduser chooses to Open instead of Save. Usually, on Windows Machines, MS Excel is by default associated with that content type.

To achieve those requirements, you need to create a CsvServlet which does basically the following in the doGet() method.

String filename = request.getPathInfo().substring(1); // get rid of leading `/`
response.setHeader("Content-Type", "text/csv");
response.setHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
PrintWriter writer = response.getWriter();
writer.append("CSV content");
// ...

That's all. The flush() and close() are by the way not strictly necessary, but useful if you want to avoid that something else further in the request chain is appending something to the response body (which should strictly not happen, but it would only emit IllegalStateExceptions and/or IOExceptions into the server logs instead of malforming the response.

Then, map the CsvServlet in web.xml with an url-pattern of /csv/* and invoke it by http://example.com/context/csv/filename.csv.

That said, you'd probably rather like a real CSV formatter/writer which nicely writes a String[][] or a List<List<String>> to an OutputStream or Writer, hereby respecting the CSV formatting rules. It might happen that a field value itself contains a quote or a comma, the CSV format would then break.

See also:

• JSP page without HTML code for exporting data to Excel Sheet

Set content type to application/vnd.ms-excel and response header for content-disposition response.setHeader("Content-Disposition", "attachment; filename=\"myfile.csv\"");