Checking attribute exists in JSP

jsp jstl jsp-tags
Javi picture Javi · Mar 26, 2010 · Viewed 73.5k times · Source

I have some classes which extends a superclass, and in the JSP I want to show some attributes of these classes. I only want to make one JSP, but I don't know in advance if the object has an attribute or not. So I need a JSTL expression or a tag which checks that the object I pass has this attribute (similar to in operator in javascript, but in the server).

<c:if test="${an expression which checks if myAttribute exists in myObject}">
    <!-- Display this only when myObject has the atttribute "myAttribute" -->
    <!-- Now I can access safely to "myAttribute" -->
    ${myObject.myAttribute}
</C:if>

How can I get this?

Thanks.

Answer

BalusC picture BalusC · Mar 26, 2010

Make use of JSTL c:catch.

<c:catch var="exception">${myObject.myAttribute}</c:catch>
<c:if test="${not empty exception}">Attribute not available.</c:if>

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