How can i check if an attribute is set (not null and not an empty string) with jstl? [duplicate]

Use the empty keyword

<c:if test="${not empty post}">
   <h3>${post.title}</h3>   
</c:if>

You can also use '!' instead 'not' :

<c:if test="${!empty post}">
    <h3>${post.title}</h3>
</c:if>