Cookies Example

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class ShoppingCartViewerCookie extends HttpServlet {

  public void doGet(HttpServletRequest req, HttpServletResponse res)
                               throws ServletException, IOException {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();

    // Get the current session ID by searching the received cookies.
    String sessionid = null;
    Cookie[] cookies = req.getCookies();
    if (cookies != null) {
      for (int i = 0; i < cookies.length; i++) {
        if (cookies[i].getName().equals("sessionid")) {
          sessionid = cookies[i].getValue();
          break;
        }
      }
    }

    // If the session ID wasn't sent, generate one.
    // Then be sure to send it to the client with the response.
    if (sessionid == null) {
      sessionid = generateSessionId();
      Cookie c = new Cookie("sessionid", sessionid);
      res.addCookie(c);
    }

  private static String generateSessionId() {
    String uid = new java.rmi.server.UID().toString();  // guaranteed unique
    return java.net.URLEncoder.encode(uid);  // encode any special chars
  }


}

• Some consider cookies a privacy threat and turn them off. We can achieve the same effect with the previous two methods.