The first thing to do is to put a hyperlink somewhere on the page where you’re logged in:

<a href="exit.jsp" target="_top"> exit </a>

Have it link to the exit.jsp page, and create a new exit.jsp page with the following code in its body:

<% session.invalidate(); %>
<jsp:forward page="login.jsp"></jsp:forward>

First log it off session, then jump to the login page, of course, you can write the page you want to jump to!