Java Keeping Track Of Cookies

Posted by admin on

September 23, 2008

I came across someone else’s code a long time ago and I thought someone else may find this useful since this class has been part of my library whenever my program involves cookies. It is a class by Saar Machtinger.

public class CookieTool {
 
  static Hashtable theCookies = new Hashtable();
 
  /**
  * Send the Hashtable (theCookies) as cookies, and write them to
  *  the specified URLconnection
  *
  * @param   urlConn  The connection to write the cookies to.
  * @param   printCookies  Print or not the action taken.
  *
  * @return  The urlConn with the all the cookies in it.
  */
  public URLConnection writeCookies(URLConnection urlConn, boolean printCookies){
    String cookieString = "";
    Enumeration keys = theCookies.keys();
 
    while (keys.hasMoreElements()) {
      String key = (String)keys.nextElement();
      cookieString += key + "=" + theCookies.get(key);
      if (keys.hasMoreElements()) cookieString += "; ";
    }
 
    urlConn.setRequestProperty("Cookie", cookieString);
 
    if (printCookies) System.out.println("Wrote cookies:\n   " + cookieString+"\n");
 
    return urlConn;
  }
 
  /**
  * Read cookies from a specified URLConnection, and insert them
  *   to the Hashtable
  *  The hashtable represents the Cookies.
  *
  * @param   urlConn  the connection to read from
  * @param   printCookies  Print the cookies or not, for debugging
  * @param   reset  Clean the Hashtable or not
  */
 
  public void readCookies(URLConnection urlConn, boolean printCookies, boolean reset) {
    if (reset) theCookies.clear();
    int i=1;
    String hdrKey;
    String hdrString;
    String aCookie;
 
    while ((hdrKey = urlConn.getHeaderFieldKey(i)) != null) {
      if (hdrKey.equals("Set-Cookie")) {
        hdrString = urlConn.getHeaderField(i);
        StringTokenizer st = new StringTokenizer(hdrString,",");
 
        while (st.hasMoreTokens()) {
          String s = st.nextToken();
          aCookie = s.substring(0, s.indexOf(";"));
          // aCookie = hdrString.substring(0, s.indexOf(";"));
          int j = aCookie.indexOf("=");
 
          if (j != -1) {
            if (!theCookies.containsKey(aCookie.substring(0, j))) {
               // if the Cookie do not already exist then when keep it,
               // you may want to add some logic to update 
               // the stored Cookie instead. thanks to rwhelan
               theCookies.put(aCookie.substring(0, j),aCookie.substring(j + 1));
 
              if (printCookies) {
                System.out.println("Reading Key: "  + aCookie.substring(0, j));
                System.out.println("        Val: " + aCookie.substring(j + 1));
              }
            }
          }
        }
      }
      i++;
    }
  }
 
  /**
  * Display all the cookies currently in the HashTable
  *
  */
  public void viewAllCookies() {
    System.out.println("All Cookies are:");
    Enumeration keys = theCookies.keys();
    String key;
    while (keys.hasMoreElements()) {
      key = (String)keys.nextElement();
      System.out.println("   " + key + "=" + theCookies.get(key));
    }
  }
 
  /**
  * Display the current cookies in the URLConnection,
  *    searching for the: "Cookie" header
  *
  * This is Valid only after a writeCookies operation.
  *
  * @param   urlConn  The URL to print the associates cookies in.
  */
  public void viewURLCookies(URLConnection urlConn) {
    System.out.print("Cookies in this URLConnection are:\n");
    System.out.println(urlConn.getRequestProperty("Cookie"));
  }
 
  /**
  * Add a specific cookie, by hand, to the HastTable of the Cookies
  *
  * @param   _key  The Key/Name of the Cookie
  * @param   _val  The Calue of the Cookie
  * @param   printCookies  Print or not the result
  */
  public void addCookie(String _key, String _val, boolean printCookies) {
    if (!theCookies.containsKey(_key)) {
      theCookies.put(_key, _val);
      if (printCookies){
        System.out.println("Adding Cookie: ");
        System.out.println("   " + _key + " = " + _val);
      }
    }
  }
}

Say for example you wish to log in to a site and want to keep your session intact when you access the site’s other pages (since they require you to be logged in). To use this class, do the following

URL url = new URL("URL_SITE_HERE");
HttpURLConnection httpcon = (HttpURLConnection) url.openConnection();
httpcon.setDoOutput(true);
 
String data = "username=" + YOUR_USERNAME + "password=" + YOUR_PASSWORD;
 
OutputStreamWriter wr = new OutputStreamWriter(httpcon.getOutputStream());
wr.write(data);
wr.flush();
wr.close();
httpcon.setInstanceFollowRedirects(false);
 
CookieTool ct = new CookieTool();
ct.readCookies(httpcon, false, false);
httpcon.disconnect();
 
ct.viewAllCookies();

We need a URL connection to set which site we want to log in to. Then specify the username and password and use the OutputStreamWriter’s write() method to emulate an HTML Form post action. The last method call, viewAllCookies() displays all data that are stored in the cookie. Please remember that the parameters passed like username and password are not the same in all sites. You should check the site’s HTML FORM tags and see what other hidden fields are included that could possible be needed in order for you to be able to logged in properly.

If you wish to access other links of the site that require you to be logged in, just use the CookieTool object ct like this

URL url = new URL("LINK_HERE");
HttpURLConnection httpcon = IMDBTool.getCookiedHttpURLConnection(ct, url);
ct.readCookies(httpcon, false, false);

You can then use the HttpURLConnection’s getInputStream() method to get the InputStream and use it to retrieve the contents of the HTML page. Getting the contents of the InputStream and storing it in a String object is another story. There is a nifty code that I use to do this (I forgot who coded this). Just go here.