Here is some sample java code.
This code returns a file from a Servlet:
package com.javaoracleblog.servlets;import java.io.*; import javax.servlet.*; import javax.servlet.http.*;/** * Servlet to download text to a file. * * @author Edwin Korsten * @version 1.0 */ public class Download extends HttpServlet {/** * Return the contents of the requested file. */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { PrintWriter out = null; try {String fileName = "test.txt"; response.setContentType("application/x-msdownload"); response.addHeader("Content-disposition", "attachment; filename=\"" + fileName + "\""); out = response.getWriter(); out.write("This is the contents of the file"); } catch (Exception e) { if (out == null) { response.setContentType("text/html"); out = response.getWriter(); } out.write("” + “Error trying to get file : “); out.write(e.toString()); out.write(”"); } out.close(); }public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { doGet(request, response); }}