Need a way to customize c:url

Question

I have a strange requirement. I use nested jsps in my application. In each of the jsps there can a number of js / and css includes. I do not want to have duplicate includes. i.e. if I have a js file included in the parent jsp, I do not want it to be included again in any of jsps imported with in the parent jsps. Is there a way to do a check for this in c:url tag? or do we have any tag that does a check of the urls included before and only then includes the new url?.
Please let me know your comments.

Answer 1

Nope thats not what the c:url tag does.
The c:url tag just formats a url and parameters for you.
It knows nothing about what urls you have used on the page before.
I think a custom tag is the way to go - in fact it would be quite simple to write as a tag file, leveraging the c:url tag.
You could declare a map/list in request scope. Anytime a script is included, you check that map for the script. If it is not there, "include" the script, and add that script to your map. If it is there, you know you have it included already.
Something like
scriptImport.tag
<%@ attribute name="src" required="true" %>
<%@ attribute name="includeMap" type="java.util.Map" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<c:if test="${not exist includeMap[src]}">
  <c:set target="${includeMap}" property="${src}" value="${src}"/>
  <script src="${pageContext.request.contextPath}${src}" type="text/javascript"></script> 
</c:if>And then use it in a jsp something like this
<jsp:useBean id="scriptUseMap" type="java.util.Map" class="java.util.HashMap" scope="request" />
<%@ taglib prefix="my" tagdir="/WEB-INF/tags %>
<my:scriptImport src="/javascript/myFunc.js" includeMap="${scriptUseMap}"/>{code}
All your imports would have to be done using this tag, using absolute includes relative to the web application root.
I think that would do what you want.
Disclaimer: this is untested code.  Its simple enough that it might work right off, but don't count on it :-)
Cheers,
evnafets