How to Block Multiple Logins /Sign Up?

1. How do I restrict concurrent login?
2. How do I avoid multiple logins on a Web application?

How do I restrict concurrent login?

Navigate to Product Settings → Connection → General Settings. Check the box next to Deny Concurrent Logins. Once enabled, the user will not be able to log in from another device at the same time. Other active sessions will not be affected by this change.

How do I avoid multiple logins on a Web application?

Easiest way is to let the User have a static Map<User, HttpSession> variable and let it implement HttpSessionBindingListener (and Object#equals() and Object#hashCode() ). User user = userDAO. find(username, password); if (user !=