Avoid whitespace in JSTL c:set statement

I have a JSP file that generates a list of LIs, where the first and the last item in the list get a special class assigned to them. I currently use the following bit for that:

<c:set var="liclass">
    <c:if test="${rowStatus.first}">first</c:if>
    <c:if test="${rowStatus.last}"> last</c:if>
</c:set>

<%-- not very pretty --%>
<li<c:if test="${not empty liclass}"> class="${liclass}"</c:if>>
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The problem in this case is that, in the case when there's only one result, the class should become 'first last' (which works), but it becomes first [...] last, where [...] represents a bunch of whitespace that SO filters away.

It seems that <c:set> also takes the whitespace caused by the indentation used. I could just solve it by typing it without whitespace:

<c:set var="liclass"><c:if test="${rowStatus.first}">first</c:if><c:if test="${rowStatus.last}"> last</c:if></c:set>

But I'd prefer the readable variant. Another alternative is to pull the result through a function that removes excess whitespace.

Question: Is there an approach or technique to avoid setting whitespace like this in a <c:set>-tag?

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I'd do it straight in value attribute with help of the conditional operator ?:.

<c:set var="liclass" value="${rowStatus.first ? 'first' : ''}" />
<c:set var="liclass" value="${liclass}${rowStatus.last ? ' last' : ''}" />

For the not pretty <li> part, I'd just add

<c:set var="liclass" value="${empty liclass ? 'none' : liclass}" />

and do

<li class="${liclass}">

True, it adds a seemingly worthless class="none" for non-first/last elements, but who cares?

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As to the concrete question, you can trim whitespace left by taglibs by setting the trimDirectiveWhitespaces attribute of the @page to true.

<%@page trimDirectiveWhitespaces="true" %>

(works in Servlet 2.5/JSP 2.1 containers only)

You can also configure it at servletcontainer level. Since it's unclear which one you're using, here's just an Apache Tomcat example: in the JSP servlet entry in Tomcat/conf/web.xml add/edit the following initialization parameter:

<init-param>
    <param-name>trimSpaces</param-name>
    <param-value>true</param-value>
</init-param>

Either way, I can't tell from top of head nor guarantee that it would achieve the desired effect of ending up with first last. You would have to give it a try yourself.