Saving Client State with Cookies and Java - Grabbing Cookies From Your Client

(Page 4 of 6 )

Extracting cookies from your client is also a straightforward process, courtesy of the Java APIs provided to us.  The acquisition process of the cookie we set using the CookieSetterServlet is shown in Listing 2. 


import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax
 .servlet
 .http
 .HttpServletRequest;
import javax
 .servlet
 .http
 .HttpServletResponse;
 
public class CookieSetterServlet
 extends HttpServlet
 implements Servlet
{
 public void doGet(
  HttpServletRequest request,
  HttpServletResponse response)
  throws ServletException, IOException
 {
  // grab the user's favorite cookie type from the request
  String favoriteCookieType =
   request.getParameter(
    "FavoriteCookiePreference");
  // report the value to the console
  System.out.println(
   "Setting favorite cookie type to: "
    + favoriteCookieType);
  // create a new Cookie object.  
  // set the token name to "FavoriteCookieType"
  // set the value to the value extracted from the request
  Cookie favoriteCookie =
   new Cookie(
    "FavoriteCookieType",
    favoriteCookieType);
  // set the value of the comment
  favoriteCookie.setComment(
   "Houses User's Favorite Cookie Type");
  // add the cookie to the response
  response.addCookie(
   favoriteCookie);
  // provide some visual feedback to the user
  PrintWriter out =
   response.getWriter();
  out.println(
   " "
    + "");
  out.println(
   " 
<H2>I am now going to "remember" that you like "
    + favoriteCookieType
    + " cookies, using Cookies.</H2>");
  out.println("");
 }
 public void doPost(
  HttpServletRequest request,
  HttpServletResponse response)
  throws ServletException, IOException
 {
  doGet(request, response);
 }
}



Listing 2: CookieSetterServlet.java

To obtain the cookie from the client, we obtain our cookies as an array of Cookie objects from the Request object.   We then have to cycle through the array, looking for the name of the cookie of our interest.  Once we find the correct cookie, we extract its value and present the value to the user (see Figure 5).

Figure 5: Output of the CookieGrabberServlet, which
Reports the Value of the Cookie Seen on the Client 

Next: Throwing JavaScript Into the (Cookie Dough) Mix >>
 

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