JSP :: How To Check If User Is Logged In

I am using form based, declarative security approach. And, when some user, on login form enters user credentials (username and password), he is being redirected to certain/secured jsp page.

Part of that page content is:Hello <%=request.getUserPrincipal().getName().toString()%> You are able to view this page because you are authorized user.You can see that this is implemented using JSP scriptlet. And this works. I would like to use JSTL instead of scriptlet.

So, instead of scriptlet, I put this JSTL code: <c:out value="${requestScope.userPrincipal.name}"/>, but not getting user's username with it. Basically, I don't clearly understand where and how are these objects/user credentials being stored with Form based JAAS.

I would like on JSP page to check if some user is already logged in. So, if there is logged user to display user's name (also with JSTL).Something like this:

<c:if test="${not empty sessionScope.userPrincipal}">
User <c:out value="${sessionScope.userPrincipal.name}" />
</c:if>

Here I tried with sessionScope but still not getting anything.