Since the request parameter used in the <c:if> tag condition was not present, the
markup in its body was not rendered. Modifying the URL so that the parameter is
there and has the expected value results in the conditional markup being rendered.
Displaying mutually exclusive markup with
the <c:choose> tag
One disadvantage of the <c:if> JSTL tag discussed in the previous section is
that there is no way to display markup if (and only if) the expression in its test
attribute evaluates to false. If we need this kind of functionality, we need the JSTL