<%
    Boolean isSignedIn = (Boolean)session.getAttribute("signedIn");
    isSignedIn = isSignedIn != null ? isSignedIn : Boolean.FALSE;
%>
<nav>
    <a href="<%= ctx %>">Home</a>
    <% if (isSignedIn) { %>
    <a href="<%= ctx %>/sign-out">Sign Out</a>
    <% } else { %>
    <a href="<%= ctx %>/sign-in.jsp">Sign In</a>
    <% } %>
</nav>