MIME type/Content-type for opening CSV files using

I have been having an issue with getting CSV output to be recognized & opened in Excel. In my web application I have a java servlet that returns search results to the user. The search results are delivered by an Apache Solr server. There is an option on the GUI front-end that allows the user to request the search results in “CSV” format. If this option is selected then the query is re-run against Solr by adding a "wt=csv" param. Then a java filter adds headers to return the results as CSV formatted-text. But it’s not working correctly.

In IE (ver 8.0) I am prompted to “Open” or “Save” the file. If I select “Open”; it just dumps CSV-formatted text on the screen instead of opening it in Excel. And if I select “Save”; I get an error message – “Unable to open this internet site. The requested site is either unavailable or cannot be found.”
In Firefox (ver 10.0.9) also; I get prompted to open or save the file. But for opening the CSV file; the default option is Notepad & Excel is not even listed. If I click “Save” then it does download the CSV file & I can open it in Excel and it’s correctly recognized by Excel.

I have tried a variety of headers & combinations –

  //((HttpServletResponse)response).setHeader("Content-Type", "application/octet; charset=utf-8");
  ((HttpServletResponse)response).setHeader("Content-Type", "text/csv");
  //((HttpServletResponse)response).setHeader("Content-Type", "application/vnd.ms-excel");
  //((HttpServletResponse)response).setHeader("Cache-Control", "private, private,max-age=0,must-revalidate");
  //((HttpServletResponse)response).setHeader("Content-Encoding", "gzip");
  //((HttpServletResponse)response).setHeader("Content-Encoding", "binary");
  ((HttpServletResponse)response).setHeader("Content-Disposition", "attachment; filename=Download.CSV");
  //((HttpServletResponse)response).setHeader("Content-Disposition", "inline; filename=Download.CSV;");

But none of them seem to be working. I used Firefox to inspect the headers that are being sent back & I see the following –

Content-Disposition:attachment; filename=Download.CSV

Content-Type:text/plain;charset=UTF-8

Server:Jetty(7.x.y-SNAPSHOT)

Transfer-Encoding:chunked

Vary:Accept-Encoding

Even though the content-type is specified as csv Or excel; when it reaches the browser it’s being interpreted as text/plain & I think that’s the issue. Not sure what header Or encoding I should be setting? Any suggestions? Thanks.

I'm doing something similar and this is part of the code I'm using:

    Date dt = new Date();
    SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd_HHmmss");
    String filename = fmt.format(dt) + ".csv";
    //Setup the output
    String contentType = "application/vnd.ms-excel";
    FacesContext fc = FacesContext.getCurrentInstance();
    HttpServletResponse response = (HttpServletResponse)fc.getExternalContext().getResponse();
    response.setHeader("Content-disposition","attachment; filename=" + filename);
    response.setContentType(contentType);

Note that I use the variable "contentType" to tell the servlet what kind of file will be generated.

Hope it works for you.