Login to website through Jsoup post method not working

Question

I have the following code which I am using to login to a website programmatically. However, instead of returning the logged in page's html (with user data info), it returns the html for the login page. I have tried to find what's going wrong multiple times but I can't seem to find it.

 public class LauncherClass {

static String username = "----username here------"; //blocked out here for obvious reasons
static String password = "----password here------";
static String loginUrl = "https://parents.mtsd.k12.nj.us/genesis/parents/j_security_check";
static String userDataUrl = "https://parents.mtsd.k12.nj.us/genesis/parents?module=gradebook";

public static void main(String[] args) throws IOException{

LauncherClass launcher = new LauncherClass();
launcher.Login(loginUrl, username, password);

}

public void Login(String url, String username, String password) throws IOException {

    Connection.Response res = Jsoup
            .connect(url)
            .data("j_username",username,"j_password",password)
            .followRedirects(true)
            .ignoreHttpErrors(true)
            .method(Method.POST)
            .userAgent("Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.4 Safari/537.36")
            .timeout(500)
            .execute();

    Map <String,String> cookies = res.cookies();

    Document loggedIn = Jsoup.connect(userDataUrl)
            .cookies(cookies)
            .get();

    System.out.print(loggedIn);

    }
}

[NOTE] The login form does have a line:

 <input type="submit" class="saveButton" value="Login">

but this does not have a "name" attribute so I did not post it

Any answers/comments are appreciated!

[UPDATE2] For the login page, browser displays the following...

 ---General
    Remote Address:107.0.42.212:443
    Request URL:https://parents.mtsd.k12.nj.us/genesis/j_security_check
    Request Method:POST
    Status Code:302 Found
----Response Headers
    view source
    Content-Length:0
    Date:Sun, 26 Jul 2015 20:06:15 GMT
    Location:https://parents.mtsd.k12.nj.us/genesis/parents?gohome=true
    Server:Apache-Coyote/1.1
----Request Headers
    view source   
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    Accept-Encoding:gzip, deflate
    Accept-Language:en-US,en;q=0.8
    Cache-Control:max-age=0
    Connection:keep-alive
    Content-Length:51
    Content-Type:application/x-www-form-urlencoded
    Cookie:JSESSIONID=33C445158EB6CCAFFF77D2873FD66BC0;         lastvisit=458D80553DC34ADD8DB232B5A8FC99CA
    Host:parents.mtsd.k12.nj.us
    HTTPS:1
    Origin:https://parents.mtsd.k12.nj.us
    Referer:https://parents.mtsd.k12.nj.us/genesis/parents?gohome=true
    User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4)                 AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.4 Safari/537.36
----Form Data
    j_username: ---username here---
    j_password: ---password here---        

Answer 1

You have to login to the site in two stages.
STAGE 1 - You send a GET request to this URL - https://parents.mtsd.k12.nj.us/genesis/parents?gohome=true and you get the session cookies.
STAGE 2 -
You send a post request with your username and password, and add the cookies you got on stage 1.
The code for that is -

Connection.Response res = null;
Document doc = null;

try {   //first connection with GET request
        res = Jsoup.connect("https://parents.mtsd.k12.nj.us/genesis/parents?gohome=true")
//                  .userAgent(YourUserAgent)
//                  .header("Accept", WhateverTheSiteSends)
//                  .timeout(Utilities.timeout)
                    .method(Method.GET)
                    .execute();         
    } catch (Exception ex) {
        //Do some exception handling here
    }
try {
        doc = Jsoup.connect("https://parents.mtsd.k12.nj.us/genesis/parents/j_security_check"")
    //          .userAgent(YourUserAgent)
    //          .referrer(Referer)
    //          .header("Content-Type", ...)
                .cookies(res.cookies())
                .data("j_username",username)
                .data("j_password",password)                    
                .post();
    } catch (Exception ex) {
        //Do some exception handling here
    }
    //Now you can use doc!

You may have to add for both requests different HEADERS such as userAgent, referrer, content-type and so on. At the end of the second request, doc should have the HTML of the site.

The reason that you cannot login to the site is that you are sending the post request without the session cookies, so it's an invalid request from the server.