Re: How to login to a site using cookie? (not applet)

Sat, 14 Jul 2007 01:32:47 -0000
On Jul 14, 2:24 am, Roedy Green <>


You simply write code to provide id/password and Java magically does
the rest.
Roedy Green Canadian Mind Products
The Java Glossary

Thanks Roedy.

What about Cookie? Firefox stores this cookie called "stn"
after I logged in, but if I delete this cookie and refresh,
I will be kicked back to the front login screen. So I think
it is the session id cookie. Don't I need to send back
a session id every time I POST?

Also, how does the Autheticator knows what are the <input>
names for the username and password? Shouldn't they be specified
somehow? (for this site, they are "LoginName" and "Password")

Below is my attempt using the Autheticator, but instead of
next_page being the string of the next page after a successful login,
it returned the front page of the site. So the method is not
successful. Do you have any idea what is wrong?

Many thanks!


My Code

public class Test2 {

    private String login_url_str = "

    public Test2() {

    public static void main(String[] args) {
        Test2 test1 = new Test2();

    private void execute() {
        //Setup for https

        Authenticator.setDefault( new MyAuthenticator() );

        try {
            URL url = new URL(login_url_str);
            //For handling POST request
            String next_page = getURLPostString(url,"");

        } catch (IOException ex) {


    /** Post a string to an URL and get the reply as a string. Returns
an empty
     string if things didn't work out. */
    //code from:
    private String getURLPostString(URL url, String body) {
        StringBuffer sb = new StringBuffer();

        // find the newline character(s) on the current system
        String newline = null;
        try {
            newline = System.getProperty("line.separator");
        } catch (Exception e) {
            newline = "\n";

        try {
            // URL must use the http protocol!
            HttpURLConnection conn = (HttpURLConnection)

            conn.setAllowUserInteraction(false); // you may not ask
the user
            conn.setDoOutput(true); // we want to send things
            // the Content-type should be default, but we set it
            // the content-length should not be necessary, but we're

            // get the output stream to POST our form data
            OutputStream rawOutStream = conn.getOutputStream();
            PrintWriter pw = new PrintWriter(rawOutStream);

            pw.print(body); // here we "send" our body!

            // get the input stream for reading the reply
            // IMPORTANT! Your body will not get transmitted if you
get the
            // InputStream before completely writing out your output
            InputStream rawInStream = conn.getInputStream();

            // get response
            BufferedReader rdr = new BufferedReader(new
            String line;

            while ((line = rdr.readLine()) != null) {
            return sb.toString();
        } catch (Exception e) {
            System.out.println("Exception " + e.toString());
        return ""; // an exception occurred


class MyAuthenticator extends Authenticator
   * Called when password authorization is needed.
   * @return The PasswordAuthentication collected from the
   * user, or null if none is provided.
   protected PasswordAuthentication getPasswordAuthentication()
      return new PasswordAuthentication ( "usernameblah",
"passwordblah".toCharArray() );

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