htmlunit - HTML Unit - login to secure website using form - can't connect to page after form -

i'm newbie java htmlunit appreciated - in advance.

i'm trying login webpage protected username , password authentication submitting username , password form on webpage using htmlunit mirror actions of web browser. website has form based authorisation.

import java.io.bufferedwriter; import java.io.file; import java.io.filewriter; import java.util.iterator; import java.util.set;  //import htmlunit classes      import com.gargoylesoftware.htmlunit.webclient; import com.gargoylesoftware.htmlunit.html.htmlform; import com.gargoylesoftware.htmlunit.html.htmlpage; import com.gargoylesoftware.htmlunit.html.htmlsubmitinput; import com.gargoylesoftware.htmlunit.html.htmltextinput; import com.gargoylesoftware.htmlunit.util.cookie;   //this class attempts submit user , password credentials //and mirrors how login button clicked on webpage:  public class submitform {      public static void main(string[] args) throws exception {          webclient webclient = new webclient();          // first page         htmlpage page1 = (htmlpage) webclient.getpage("http://cmdbjr/frameset.php?ci_name=&ci_id=&ci_type=");          // form dealing , within form,         // find submit button , field want change.         htmlform form = page1.getformbyname("loginform");          // enter login , passwd         form.getinputbyname("user_id").setvalueattribute("#####");         form.getinputbyname("password").setvalueattribute("#####");          // click "sign in" button/link         page1 = (htmlpage) form.getinputbyvalue("log in").click();          // added cookie section returns null pointer exception             set<cookie> cookie = webclient.getcookiemanager().getcookies();          if(cookie != null){              iterator<cookie> = cookie.iterator();              while (i.hasnext()) {                  webclient.getcookiemanager().addcookie(i.next());              }          }           //  page html         string htmlbody = page1.getwebresponse().getcontentasstring();         //  save response in file         string filepath = "c:/temp/test_out.html";          bufferedwriter bw = new bufferedwriter(new filewriter(new file(filepath)));         bw.write(htmlbody);         bw.close();          // change value of text field         // userfield.setvalueattribute("alwalsh");         // passwordfield.setvalueattribute("1reland6");          // submit form clicking button , second page.         // final htmlpage page2 = button.click();           webclient.closeallwindows();     } } 

if run code without cookie section of code page trying reach after login page doesn't appear error page appears saying i'm not connected internet.

if code run cookie section error:

exception in thread "main" >java.lang.nullpointerexception @ contentweb.main(contentweb.java:26)

is returned.

i'm new java htmlunit @ appreciated. in advance.

i replicated example yahoo mail login credentials , worked. however, added : webclient.setthrowexceptiononscripterror(false); ignore exceptions on script errors.