Check if parameter exists in Expression Language
el, jsp, jstl, parameters
Solution
Use the `not empty` check.
<c:if test="${not empty param.username}" >
</c:if>
Edit: If you have a parameter of the form `?username` (no value), it is safer to use `${param.username ne null}`
Problem
``` <c:if test="${param.username}" > </c:if> ``` How do I check if param.username exists??