Can there possibly be more than one admin in the DB? I'm asking because the code loops through all results, and only then executes the JSP code that tests the username and password. So effectively it only looks at the last record from the DB, not all of them.
Another point is that you're only handling the cases of either a match in both username and password, or in neither of them. What should happen if the usernames match, but not the passwords (or vice versa)?