Can't use standard jaas form based authentication

In vaadin 6 we’re used form based auth. After migration on vaadin7 it broke.
On vaadin6, when u going on secure url “/blahblah/” without authentication u’ll get login form response. I think u’re guys know how works form based authentication in java standard. But in vaadin7 application still trying to load itself and throwing exception “cant get ./VAADIN/vaadinBootstrap.js”, it’s normal coz vaadin trying to access secure resource.

What’s going on ? What i should to do for form based auth starts to work? It’s really important.