How to pass a reference to a file from Java in xpages

Question

I am sorry for my English. I use a translator. There is a code to Java. Reads from the database of the field Posgresql bytea binary data and stores it in a file:

<code>
    public static void saveToFile() throws IOException {
    try {
    Connection conn = JdbcUtil.getConnection(FacesContext.getCurrentInstance(), "derby1");
            ResultSet rs = conn.createStatement().executeQuery(
                            "SELECT files FROM test_goverment where who='d'");
            byte[] imgBytes = null;
            if (rs != null) {
                while (rs.next()) {
                    imgBytes = rs.getBytes(1);
                }
                FileOutputStream os = new FileOutputStream("c:\\samoutput.txt");
                os.write(imgBytes);
                os.flush();
                os.close();
            }
            rs.close();
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        enter code here}
    }
</code>

How to transfer the file to download to user in Xpages. And remove it after downloading.

Answer 1

You just want to transfer the query result to browser client for download and don't want to save it.

Instead of saving the query result to a file first and transfer it for download later
you can stream the content direct to XPage's response like this:

public static void downloadFile() throws IOException {
    try {
        FacesContext facesContext = FacesContext.getCurrentInstance();
        Connection conn = JdbcUtil.getConnection(facesContext, "derby1");
        ResultSet rs = conn.createStatement().executeQuery(
                            "SELECT files FROM test_goverment where who='d'");
        byte[] imgBytes = null;
        if (rs != null) {
            while (rs.next()) {
                imgBytes = rs.getBytes(1);
            }
            ExternalContext extCon = facesContext.getExternalContext();
            XspHttpServletResponse response = (XspHttpServletResponse)extCon.getResponse();
            response.reset();
            response.setContentType("text/plain");
            response.setHeader("Content-disposition", "attachment; filename=output.txt");
            response.setHeader("Cache-Control", "no-cache");
            OutputStream os = response.getOutputStream();
            os.write(imgBytes);
            os.flush();
            facesContext.responseComplete();
            rs.close();              
        }
        conn.close();
    } catch (SQLException e) {
        e.printStackTrace();
    }
}

You might also have a look at this XSnippet. It shows you how to present files for download in case you want/have to stay with files instead just streams.