How to debug JSTL?

I'm using SpringSource Tool Suite (with Roo) and have some success. What bothers me though is that I don't know how to debug tag library-stuff.

I may add breakpoints but it never stops at them.

What I'm looking for is a dump of all current variables in the context.

Up until now I did something like:

<c:forEach items="${data}" var="item">
    <c:out value="${item}"></c:out><br />
</c:forEach>

Sadly, that's difficult to read and also not pretty straightforward.

What can I do to improve this?