There is information missing here. The only way that "/abc" can be a "login page" is if you deployed the webapp at the root context and have mapped a
servlet to the URL "/abc".
Of course, it also implies that you are using a user-designed "insecurity" system. I call it that, because I've worked with webapps in many environments for many years and have never yet seen a user-designed system that was actually secure.
The only real way you can block access to a login is to do something like filter out attempts from unauthorized client IP addresses. Until you log in, the app will have no way of knowing who the user is, and therefore no way of knowing whether the user is permitted to log in. The prescience module for Tomcat is currently broken.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.