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is a variable set?

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Join Date: Oct 2004

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Posting Whiz

is a variable set?

Apr 27th, 2005

I am in the process of learning JSP and my question is how do I check to see if a variable exists? The equivalent of this in php would be
[php]if (isset($_POST['someVar']))[/php] or
[php]if (isset($_GET['someVar']))[/php]
any and all help would be appreciated!

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Join Date: Dec 2004

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Taboo Programmer

Re: is a variable set?

Apr 27th, 2005

I'm pretty sure you can use defined in javascript. You can try:

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if (defined(somevariable)) {
   alert(somevariable);
}
if (defined(somevariable)) {
   alert(somevariable);
}

I'm not sure, but I think that's accurate.

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Join Date: Oct 2004

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Posting Whiz

Re: is a variable set?

Apr 28th, 2005

that wont work because i need it to be serverside, otherwise i might as well do it in html/javascript instead of jsp

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Join Date: Dec 2004

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Taboo Programmer

Re: is a variable set?

Apr 28th, 2005

You are talking about a regular variable right? Or are you talking about an evirionment variable?

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duckman

Re: is a variable set?

Apr 28th, 2005

You mean a request or session attribute?
It's easy.

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<c:if test="${not empty someVar}">
  <%-- do what you need to do when the attribute is there --%>
</c:if>
<c:if test="${not empty someVar}">
  <%-- do what you need to do when the attribute is there --%>
</c:if>

Actually if it's just to prevent errors when outputting something you don't need to check, JSTL is smart enough to ignore anything that's not there so

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