How to submit a form in a web

Question

Hi, it's my first post in this forum and it's for asking a very rough problem.
I want to log in a web which uses a form to authenticate. The page is: https://cv2008.uab.cat. I want that my program in java logs in and retrieves information from it (e.g. downloading a file). I've been studying the form and it uses POST method and requires to fill the username and password fields. Moreover I've found something interesting in the form:
<input type="hidden" name="lt" value="_c23CA00BA-41D7-8934-6F3E-D754BD70ECBE_kAAFD1C38-B06B-2F6E-776D-92949E17286F" />
                              <input type="hidden" name="_eventId" value="submit" />
but I don't know what to do with it.
Well, about the app, I've been trying to use common httpclient and the.net libs but I couldn't log in.
Here is my last try:
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.PostMethod;
public class HttpClientTutorial {
    public static void main(String[] args){
         HttpClient client = new HttpClient();     
         String response = null;
         PostMethod authPost = new PostMethod("https://sac.uab.cat/login?service=https://cv2008.uab.cat/home/");
         NameValuePair[] data = {
                   new NameValuePair("username", "MY_USER"),
                   new NameValuePair("password", "MY_PASS"),
                   new NameValuePair("lt", "_c23CA00BA-41D7-8934-6F3E-D754BD70ECBE_kAAFD1C38-B06B-2F6E-776D-92949E17286F"), 
                   new NameValuePair("_eventId", "submit"), 
                   new NameValuePair("submit","submit")
         authPost.setRequestBody(data);
         try {
              client.executeMethod(authPost); 
              response = authPost.getResponseBodyAsString();
              System.out.println(authPost.getStatusCode());
         catch(Exception e)
              System.out.println("Error");
         authPost.releaseConnection();
         System.out.println(response);
}I'd appreciate any help, thank you!
Kits

Answer 1

Hey malcolmmc,
you were right, that eventId field changes every time I make a client.executemethod(authPost); the problem is that I need to do it to retrieve the value of that field but after I make the authPost.setRequestBody(data); with the information to fill the form, I need to execute the method again and then the value has changed again. So, I need to retrieve the value and "without closing that session" send the form. But I don't know how to do it, I think I'm very close to achieve it 'though!
My code rightnow is:
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.NameValuePair;
import org.apache.commons.httpclient.methods.PostMethod;
public class HttpClientTutorial {
     public static String search_lt(String content) {
         String ltValue = "";
         String lt = "lt\" value=\"";
         int i = 0;
         boolean foundIt = false;         
         int max = content.length() - lt.length();
         test:
             for(i = 0; i <= max; i++) {
                 int n = lt.length();
                 int j = i;
                 int k = 0;
                 while (n-- != 0) {
                     if (content.charAt(j++)
                             != lt.charAt(k++)) {
                         continue test;
                 foundIt = true;
                      break test;
          if (foundIt == true)
               i = i + lt.length();                   
               while (content.charAt(i) != '\"') {
                    ltValue = ltValue + content.charAt(i);
                    i++;
          else
               System.out.println("Not Found.");
          return ltValue;
    public static void main(String[] args){
         String response, ltValue;
         HttpClient client = new HttpClient();          
         PostMethod authPost = new PostMethod("https://sac.uab.cat/login?service=https://cv2008.uab.cat/sessioCAS/usuari.jsp");
        try {
             response = authPost.getResponseBodyAsString();
             ltValue = search_lt(response);
              NameValuePair[] data = {
                        new NameValuePair("username", "MY_USER"),
                        new NameValuePair("password", "MY_PASS"),
                        new NameValuePair("lt", ltValue), 
                        new NameValuePair("_eventId", "submit"), 
                        new NameValuePair("submit","INICIAR SESSIÓ")
              authPost.setRequestBody(data);
              client.executeMethod(authPost); 
              response = authPost.getResponseBodyAsString();
              ltValue = search_lt(response);
              System.out.println(authPost.getStatusCode());
              authPost.releaseConnection();
             System.out.println(response);
        catch(Exception e) {
             System.out.println("Error");
}{code}
Thank you for the help!