Need help logging into website and retrieving information

问题

I have read through many similar questions, but I am still stuck with logging in to my school gradebook (https://parents.mtsd.k12.nj.us/genesis/parents) to retrieve data. My networking class is shown below:

public class WebLogin {

    public String login(String username, String password, String url) throws IOException {
        URL address = new URL(url);

        HttpURLConnection connection = (HttpURLConnection) address.openConnection();
        connection.setDoOutput(true);
        connection.setRequestProperty("j_username", username);
        connection.setRequestProperty("j_password", password);
        connection.setRequestProperty("__submit1__","Login");

        InputStream response = connection.getInputStream();
        Document document = Jsoup.parse(response, null, "");

        //don't know what to do here!

        return null;
    }
 }

I am not sure what to do with the InputStream or if I am going about logging in correctly, and once again, I have gone through and read several online resources to try to understand this concept but I am still confused. Any help is appreciated!

UPDATE: So now I understand the basic process and I know what I have to do. When using Jsoup to handle the connection, I know you can do something like this:

    Connection.Response res = Jsoup.connect("---website---")
                .data("j_username", username, "j_password", password)
                .followRedirects(true)
                .method(Method.POST)
                .execute();

However, I am still a little confused as to how to actually send the data (such as a user's username/password to the website with HttpURLConnection, and how to actually store the obtained cookie...otherwise, the help has been really useful and I am fine with everything else

回答1:

EXAMPLE HOW-TO:

(explanation on the origin in edit part)

connect to website (login page) with user creditentials [with HttpUrlConnection]
grab cookies
reconnect to page with user data
parse data [with JSoup]
present

(with use of value/key pair with http url connection):

1-2 . assuming we got some URL adress (login page "http://blabla/login.php") & we wanna login so what we do:

// create  & open connection 
HttpUrlConnection connection = (HttpURLConnection) new URL(adress).openConnection();

// set do output ...
connection.setDoOutput(true);

/** variable charset for encoding */
String CHARSET = "UTF-8";

// Construct the POST value/key pair  data.
String data = "login=" + URLEncoder.encode(login, CHARSET)      
        + "&password=" + URLEncoder.encode(password, CHARSET) 
        + "&remember_me=on";

byte[] dataBytes = data.getBytes(CHARSET);

// create output stram to write our creditentials 
OutputStream outputStream = new BufferedOutputStream(connection.getOutputStream());

// write value/key data to output stream
outputStream.write(dataBytes);
outputStream.flush();

// connect to url 
connection.connect();

// now we are connected and we can do other stuff get input strem header response code etc....
int responseCode = connection.getResponseCode();

 /**
 *     here we grab cookies (how?  - in other story)
 */

connection.disconnect();

3 . THEN WE GOT SECOND PAGE WITH USER DATA ( http://blabla/userdata.php ) (*if we allready were not redirected, ** we also can reuse connection or do request as next step to above)

//we are creating & oppening another connection to new adres as at beginning 
HttpUrlConnection connection = (HttpURLConnection) new URL(adressToUserData).openConnection();

// but we do not construct user value/kay data & don't create output stream 
// we just add obtained cookies as request property 
connection.addRequestProperty("Cookie", _cookie); 

//connecting
connection.connect();

//getting input stram 
InputStrem is = connection.getInputStream();

//parse data for example with jsoup 
Document doc = JSoup.parse(is,null"");

//show parsed result example in grid view

to parse data you need to know the structure of web page after login (the part with user grades) to examine a page u can use simple tool built in chrome web browser (right click with mouse & examine element)

then u got the "page" as document from point 3 & u select what u need

Elements tableWithGrades = doc.select("table>grades");

u cant select single element as table row(tr), cell(td), span, div by id or class, name etc from HTML - what u like to. You just need to learn 'syntax' of JSoup & got 'simple' knowledge of html:)

EDIT:

"I am not sure what to do with the InputStream or if I am going about logging in correctly, and once again, I have gone through and read several online resources to try to understand this concept but I am still confused."

to be clear:

you need to made yourself clear objective(goals) - what you want to achieve
then the way how.

You want to (--goals--):

present data from school server which are avaliable for logged in user

so u need to ACT & "THINK" like a WEB BROWSER:(--way--):

make request with user creditentials (login)
grab data for logged in user
parse data (get what u want from the data)
show results

u know now how to do 1,2 from my previous answers

u need now think how-to 3,4 - there are many ways - many roads to one place :P it's your choice which one will u take - but still you need to be aware of those roads :)

so what part of gathered data & in what kind of way u want to present it ?

EDIT2:

"However, I am still a little confused as to how to actually send the data (such as a user's username/password to the website with HttpURLConnection"

by implementing a login form (activity) which will gather user data
providing data from any other source (as u desired)

before u call:

// change post string "?login=xxxx&password=zzz" to byte array *
byte[] dataBytes = data.getBytes(CHARSET);

which is bound with:

//write value/key data to output stream
outputStream.write(dataBytes);
outputStream.flush();

or before u call as in yr jsoup example:

res.execute();

u need to set String login="...";, passwod="...." why???

because your code is called sequential(excluding parareel parts) & java use references

"and how to actually store the obtained cookie..."

use persisten storage like: shared preferences, file, database
or for session(per app 'pid=vm' lifecycle) singleton instance(example Application class or any other singleton) or some helper class / variable which will not be consumed by GC during your session

"and does writing to the outputStream do the same thing as what my Jsoup example would do? "

in your statment jsoup uses so known builder pattern which makes the same as code i wrote in point 1-4 but it's something like: "the details on how you do it are not irrelevant to me as far it is working" as you can dig a hole with an ax or a shovel - you get the expected result.

"when you are posting login information, why would that be an encoded param?"

imagine your password looks like this $$$s-_xxx.php?xxaasfs??dfsdfśś%%___////**"* - try to do browser request with that kinnd of url http://server.com/home.php&action=login&username=xxx&password=$$$s-_xxx.php?xxaasfs??dfsdfśś :)))

URLEncoder.encode(password, CHARSET) 

/**
* This class is used to encode a string using the format required by
* {@code application/x-www-form-urlencoded} MIME content type.
*
* <p>All characters except letters ('a'..'z', 'A'..'Z') and numbers ('0'..'9')
* and characters '.', '-', '*', '_' are converted into their hexadecimal value
* prepended by '%'. For example: '#' -> %23. In addition, spaces are
* substituted by '+'.
*/

SOME OTHER HINTS:

when u open a stream you should close it when u're done
to close stream 'best way' (not always) is to use finally block of try/catch
befor you poceed with stram check if it is not null it will save your time
if u use jsoup check for elements.size()>0 or element!=null before u perform any strings/element involving actions

ps. for youre case you should look also at

Using Form-Based Login in JavaServer Faces Web Applications

I hope that this will give you an overview of one of the possible paths & sorry for typos i dont know english language ;p at all

回答2:

One way to do this is using Apache Http Client. Maybe something like below could work.

Request.Post("https://parents.mtsd.k12.nj.us/genesis/j_security_check")
    .bodyForm(
        Form.form()
        .add("j_username",  username)
        .add("j_password",  password).build()
    )
.execute().returnContent();

You'll have figure out what information are necessary for logging in (URL, request method, name and value of parameters etc.).

Here is an example I found for logging into Gmail.

来源：https://stackoverflow.com/questions/31629938/need-help-logging-into-website-and-retrieving-information

标签

java

httpurlconnection