How to fill a form with Jsoup?

You want to use FormElement. This is a useful feature of Jsoup. It is able to find the fields declared inside a form and post them for you. Before posting the form you can set the value of the fields using Jsoup API.

Nota:

In the sample codes below, you'll always see calls to the Element#select method followed by a call to Elements#first method.

For example : responseDocument.select("form#aspnetForm").first()

Jsoup 1.11.1 has introduced a more efficient alternative : Element#selectFirst. You can use it as a direct replacement of the original alternative.

For example:
responseDocument.select("form#aspnetForm").first()
can be replaced by
responseDocument.selectFirst("form#aspnetForm")

SAMPLE CODE

// * Connect to website
String url = "http://kepler.sos.ca.gov/";
Connection.Response resp = Jsoup.connect(url) //
                                .timeout(30000) //
                                .method(Connection.Method.GET) //
                                .execute();

// * Find the form
Document responseDocument = resp.parse();
Element potentialForm = responseDocument.select("form#aspnetForm").first();
checkElement("form element", potentialForm);
FormElement form = (FormElement) potentialForm;

// * Fill in the form and submit it
// ** Search Type
Element radioButtonListSearchType = form.select("[name$=RadioButtonList_SearchType]").first();
checkElement("search type radio button list", radioButtonListSearchType);
radioButtonListSearchType.attr("checked", "checked");

// ** Name search
Element textBoxNameSearch = form.select("[name$=TextBox_NameSearch]").first();
checkElement("name search text box", textBoxNameSearch);
textBoxNameSearch.val("cali");

// ** Submit the form
Document searchResults = form.submit().cookies(resp.cookies()).post();

// * Extract results (entity numbers in this sample code)
for (Element entityNumber : searchResults.select("table[id$=SearchResults_Corp] > tbody > tr > td:first-of-type:not(td[colspan=5])")) {
    System.out.println(entityNumber.text());
}

public static void checkElement(String name, Element elem) {
    if (elem == null) {
        throw new RuntimeException("Unable to find " + name);
    }
}

OUTPUT (as of this writing)

C3036475
C3027305
C3236514
C3027304
C3034012
C3035110
C3028330
C3035378
C3124793
C3734637

See also:

In this example, we will log into the GitHub website by using the FormElement class.

// # Constants used in this example
final String USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"; 
final String LOGIN_FORM_URL = "https://github.com/login";
final String USERNAME = "yourUsername";  
final String PASSWORD = "yourPassword";  

// # Go to login page
Connection.Response loginFormResponse = Jsoup.connect(LOGIN_FORM_URL)
                                             .method(Connection.Method.GET)
                                             .userAgent(USER_AGENT)
                                             .execute();  

// # Fill the login form
// ## Find the form first...
FormElement loginForm = (FormElement)loginFormResponse.parse()
                                         .select("div#login > form").first();
checkElement("Login Form", loginForm);

// ## ... then "type" the username ...
Element loginField = loginForm.select("#login_field").first();
checkElement("Login Field", loginField);
loginField.val(USERNAME);

// ## ... and "type" the password
Element passwordField = loginForm.select("#password").first();
checkElement("Password Field", passwordField);
passwordField.val(PASSWORD);        


// # Now send the form for login
Connection.Response loginActionResponse = loginForm.submit()
         .cookies(loginFormResponse.cookies())
         .userAgent(USER_AGENT)  
         .execute();

System.out.println(loginActionResponse.parse().html());

public static void checkElement(String name, Element elem) {
    if (elem == null) {
        throw new RuntimeException("Unable to find " + name);
    }
}

All the form data is handled by the FormElement class for us (even the form method detection). A ready made Connection is built when invoking the FormElement#submit method. All we have to do is to complete this connection with addional headers (cookies, user-agent etc) and execute it.